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LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 

Class 


MARCONI    WIRELESS    TELEGRAPH    STATION,    CLIFDEN,    IRELAND 

Photographed  at  night  while  sending  a  message  across  the  Atlantic. 

The  terrific  snapping  of  the  electric  discharge  is  heard  by  one 
standing  near  the  station,  but  no  light  is  seen.  The  strange  light 
given  out  from  the  network  of  wires  is  invisible  to  the  eye,  but  is 
caught  by  the  photographic  plate. 


THE    SAME    STATION    PHOTOGRAPHED    BY    DAYLIGHT 


7 


THE   STORY   OF 
GREAT   INVENTIONS 


BY 

ELMER    ELLSWORTH    BURNS 

*  INSTRUCTOR  IN  PHYSICS  IN  THE 

JOSEPH  MEDILL  HIGH  SCHOOL,  CHICAGO 


WITH    MANY    ILLUSTRATIONS 


HARPER  &  BROTHERS  PUBLISHERS 

YORK     AND     LONDON 
M  CMX 


gcccocccccoooocooosppoocccccccccoeooaooa 


Copyright,  1910,  by  HARPER  &  BROTHERS 

Published  November,  IQIO. 
Printed  in  the  United  States  of  America 


CONTENTS 

CHAPTER  I 

THE   AGE    OF   ARCHIMEDES 

Archimedes  the  first  great  inventor. — The  battle  of  Syracuse. — Archi- 
medes' principle. — Inventions  of  the  ancient  Greeks  .  .  .  Page  i 

CHAPTER  II 

THE   AGE    OF   GALILEO 

Galileo  and  the  battle  for  truth. — The  pendulum  clock. — Galileo's  ex- 
periment with  falling  shot. — The  telescope. — Galileo's  struggle. — 
Torricelli  and  the  barometer. — Otto  von  Guericke  and  the  air-pump. — 
Robert  Boyle  and  the  pressure  of  air  and  steam. — Pascal  and  the 
hydraulic  press. — Newton. — Gravitation. — Colors  in  sunlight  .  Page  9 

CHAPTER  III 
THE   EIGHTEENTH   CENTURY 

James  Watt  and  the  steam-engine. — The  first  steam-engine  with  a  piston. 
— Newcomen's  engine. — Watt's  engine. — Horse-power  of  an  engine. — 
The  Leyde.n  jar. — Conductors  and  insulators. — Two  kinds  of  electric 
charge.  —  Franklin's  kite  experiment.  —  The  lightning-rod. — Galvani 
and  the  electric  current. — Volta  and  the  electric  battery  .  .  Page  34 

CHAPTER  IV 
FARADAY   AND   THE    FIRST    DYNAMO 

Count  Rumford. — Count  Rumford's  experiment  with  the  cannon. — Davy. 
— Faraday's  electrical  discoveries. — Oersted  and  electromagnetism. — 
Ampere. — Arago. — Faraday's  first  electric  motor. — An  electric  current 
produced  by  a  magnet. — Detecting  and  measuring  an  electric  current. 
— An  electric  current  produced  by  the  magnetic  field  of  another  cur- 
rent.— Faraday's  dynamo. — A  wonderful  law  of  nature  .  ,  Page  55 

V 


235469 


CONTENTS 


CHAPTER  V 

GREAT  INVENTIONS  OF  THE  NINETEENTH  CENTURY 
Electric  batteries. — The  dry  battery. — The  storage  battery. — The  dy- 
namo.— Siemens'  dynamo. — The  drum  armature. — Edison's  compound- 
wound  dynamo. — Electric  power. — The  first  electric  railway. — Electric 
lighting. — The  telegraph. — Duplex  telegraphy. — The  telephone. — The 
phonograph. — Gas-engines. — The  steam  locomotive. — How  a  locomo- 
tive works. — The  turbine Page  88 

CHAPTER  VI 

THE   TWENTIETH-CENTURY   OUTLOOK 

Air-ships. — The  aeroplane. — How  the  Wright  aeroplane  is  kept  afloat. — 
Submarines. — Some  spinning  tops  that  are  useful. — The  monorail-car. 
— Liquid  air  and  the  greatest  cold. — The  electric  furnace  and  the 
greatest  heat.  —  The  wireless  telegraph — The  wireless  telephone. — 
Wonders  of  the  alternating  current. — X-rays  and  radium  .  Page  173 

APPENDIX 
Brief  notes  on  important  inventions Page  237 

INDEX Page  247 


ILLUSTRATIONS 


FIG.  PAGE 

MARCONI  WIRELESS-TELEGRAPH  STATION,  CLIFDEN,  IRELAND  ) 
THE    SAME    STATION    PHOTOGRAPHED    BY    DAYLIGHT         .       .         ) 

I THE    BATTLE     OF     SYRACUSE 3 

2 — GALILEO'S  PENDULUM  CLOCK n 

3 AN  AIR  THERMOMETER 14 

4 TORRICELLl'S  EXPERIMENT 19 

5 — GUERICKE'S  AIR-PUMP       .     .     . 22 

6 — GUERICKE'S  WATER  BAROMETER 24 

7 A  LIFT-PUMP 25 

8 A    SIMPLE    HYDRAULIC    PRESS 26 

9 HOW    AN    HYDRAULIC    PRESS    WORKS 28 

IO AN    HYDRAULIC    PRESS    WITH    BELT-DRIVEN    PUMP 29 

ii — NEWTON'S  EXPERIMENT  WITH  THE  PRISM  .           32 

12 — PAPIN'S  ENGINE » 36 

13 THE     NEWCOMEN  ENGINE,  IN  REPAIRING  WHICH  WATT  WAS  LED 

TO  HIS  GREAT  DISCOVERIES 39 

14 CYLINDER  OF  WATT'S  STEAM-ENGINE 41 

15 A  FLY-BALL  GOVERNOR 42 

l6 A    LEYDEN    JAR 43 

17 — FRANKLIN'S  KITE  EXPERIMENT 47 

l8 VOLTA  EXPLAINING  HIS  ELECTRIC  BATTERY  TO  NAPOLEON  BONA- 
PARTE   52 

19 THE    FIRST    ELECTRIC    BATTERY           54 

20 — COUNT    RUMFORD'S    EXPERIMENT   WITH   THE    CANNON,    MAKING 

WATER    BOIL    WITHOUT    FIRE 60 

21 — OERSTED'S  EXPERIMENT 66 

22 A  COIL  WITH  A  CURRENT  FLOWING  THROUGH  IT  ACTS  LIKE  A 

MAGNET 67 

23 A  BAR  OF  SOFT  IRON  WITH  A  CURRENT  FLOWING  AROUND  IT  BE- 
COMES A  MAGNET 67 

24 TWO  COILS  WITH  CURRENTS  FLOWING  IN  THE  SAME  DIRECTION 

ATTRACT  EACH  OTHER 68 

25 TWO  COILS  WITH  CURRENTS  FLOWING  IN  OPPOSITE  DIRECTIONS 

REPEL  EACH  OTHER 68 

26 ARAGO'S    EXPERIMENT           ,,,,...  70 


ILLUSTRATIONS 


FIG.  PAGE 

27 ONE  POLE  OF  A  MAGNET  SPINS  ROUND  A  WIRE  THROUGH  WHICH 

AN  ELECTRIC  CURRENT  FLOWS 71 

28 WHEN  A  MAGNET  IS  THRUST  INTO  A  COIL  OF  WIRE  IT  CAUSES  A 

CURRENT  TO  FLOW  IN  THE  COIL,  BUT  THE  CURRENT  FLOWS 

ONLY  WHILE  THE  MAGNET  IS  MOVING 73 

29 A  COIL  OF  WIRE  AROUND  A  COMPASS-NEEDLE 74 

30 — FARADAY'S  INDUCTION-COIL 76 

31 HISTORICAL  APPARATUS  OF  FARADAY  IN  THE  ROYAL  INSTITUTION  77 

32 — FARADAY'S  FIRST  DYNAMO 78 

33 — FARADAY'S    LABORATORY,    WHERE    THE    FIRST    DYNAMO    WAS 

MADE 79 

34 THE  FIRST  TRANSFORMER 80 

35 — THE    "MAGNETIC    FIELD"    is   THE    SPACE    AROUND    A    MAGNET 

IN  WHICH  IT  WILL  ATTRACT  IRON 8l 

36 MAGNETIC  FIELD  OF  A  HORSESHOE  MAGNET       .     .     .     .    .     .  8l 

37 A  DANIELL  CELL 90 

38 A  GRAVITY  CELL 91 

39 SHOWING  WHAT  IS  IN  A  DRY  BATTERY 92 

40 A  STORAGE  BATTERY,   SHOWING  THE   "  GRIDS " 94 

41 A  STORAGE-BATTERY  PLATE  MADE  FROM  A  SHEET  OF  LEAD  .     .  95 

42 — STURGEON'S  ELECTROMAGNET 97 

43 AN  ELECTROMAGNET  WITH  MANY  TURNS  OF  INSULATED  WIRE  .  98 

44 AN  ELECTROMAGNET    LIFTING  TWELVE  TONS  OF  IRON       ...  99 

45 A  DYNAMO  WITS  SIEMENS*  ARMATURE 1OI 

46 RING  ARMATURE IO2 

47 FIRST  DYNAMO  PATENTED  IN  THE  UNITED  STATES       ....  103 

48 A   DRUM   ARMATURE,    SHOWING    HOW    AN    ARMATURE   OF   FOUR 

COILS  IS  WOUND 104 

49 A  SERIES-WOUND  DYNAMO IO6 

50 A  SHUNT-WOUND  DYNAMO 107 

51 A  COMPOUND-WOUND  DYNAMO IO8 

52 — ONE  OF  EDISON'S  FIRST  DYNAMOS 109 

53 A  DYNAMO  MOUNTED  ON  THE  TRUCK  OF  A  RAILWAY  CAR  .     .     .  HO 

54 FIRST  ELECTRIC   LOCOMOTIVE 113 

55 FIRST  EDISON  ELECTRIC  LOCOMOTIVE 115 

56 — EDISON'S  FIRST  PASSENGER  LOCOMOTIVE 117 

57 FIRST  COMMERCIAL  ELECTRIC  RAILWAY 119 

58 — EDISON,    AMERICA'S    GREATEST    INVENTOR,    AT    WORK    IN    HIS 

LABORATORY 122 

59 — EDISON'S  FAMOUS  HORSESHOE  PAPER-FILAMENT  LAMP  OF  1870.  123 
60 FIRST    COMMERCIAL    EDISON    ELECTRIC-LIGHTING    PLANT;     IN- 
STALLED ON  THE  STEAMSHIP  "COLUMBIA"  IN  MAY,  1880  .  125 

6l A  TELEGRAPH  SOUNDER .....,,,  129 

viii 


ILLUSTRATIONS 


FIG.  PAGE 

62 — MORSE'S  FIRST  TELEGRAPH  INSTRUMENT 131 

63 A    TELEGRAPHIC    CIRCUIT    WITH    RELAY    AND    SOUNDER.       .       .       .  132 

64 A    SIMPLE    TELEGRAPHIC    CIRCUIT           133 

65 FIRST   TELEGRAPH   INSTRUMENT    USED    FOR   COMMERCIAL   WORK    .  135 

66 HOW    TWO    MESSAGES    ARE    SENT    OVER    ONE    WIRE    AT    THE    SAME 

TIME 137 

67 HOW  TWO  MESSAGES  ARE  SENT  OVER  ONE  WIRE  AT  THE  SAME 

TIME.     BRIDGE  METHOD    ....'.. 139 

68 FIRST  BELL  TELEPHONE  RECEIVER  AND  TRANSMITTER     .     .     .  142 

69 A  TELEPHONE  RECEIVER 143 

70 TWO  RECEIVERS  USED  AS  A  COMPLETE  TELEPHONE     ....  145 

71 CARBON-DUST  TRANSMITTER • 146 

72 THE  PHONAUTOGRAPH,   A  FORERUNNER  OF  THE  PHONOGRAPH  .  149 

73 — EDISON'S  FIRST  PHONOGRAPH  AND  A  MODERN  INSTRUMENT      .  150 

74  tO  77 THE  FOUR-CYCLE  GAS-ENGINE 152 

78 TWO-CYCLE    GAS-ENGINE.     CRANK   AND    CONNECTING-ROD   ARE 

ENCLOSED  WITH  THE  PISTON     .     .     .     .     .     ,  ".     .     .     .  154 
79 — SELDEN   "EXPLOSION  BUGGY,"   FORERUNNER  OF  THE   MODERN 

AUTOMOBILE 155 

80 SOME  EARLY  LOCOMOTIVES 158 

8 1 HOW    A    LOCOMOTIVE    WORKS l6l 

82 — HERO'S  ENGINE * 164 

83 AN  UNDERSHOT  WATER-WHEEL  WITH  CURVED  BLADES     .      .     .  165 

84 AN  OVERSHOT  WATER-WHEEL 1 66 

85 DE  LAVAL  STEAM-TURBINE       167 

86 A  MODERN  STEAM-TURBINE  WITH  TOP  CASING  RAISED  SHOWING 

BLADES           l68 

87 DIAGRAM    OF    TURBINE    SHOWN    IN    FIG.    86 169 

88 A  STEAM-TURBINE  THAT  RUNS  A  DYNAMO  GENERATING  I4,OOO 

ELECTRICAL  HORSE-POWER 170 

89 BRITISH  ARMY  AIR  -  SHIP  "NULLI  SECUNDUS"  READY  FOR 

FLIGHT 176 

90 BASKET,  MOTOR,  AND  PROPELLER ,  OF  THE  BRITISH  ARMY  AIR- 
SHIP "NULLI  SECUNDUS" 178 

91 A    ZEPPELIN    AIR-SHIP l8l 

92 — COUNT   ZEPPELIN'S    "DEUTSCHLAND,"    THE    FIRST    AIR-SHIP   IN 

REGULAR  PASSENGER  SERVICE 182 

93 THE  BALDWIN  AIR-SHIP  USED  IN  THE  UNITED  STATES  ARMY  .     .  183 

94 — IN  FULL  FLIGHT 185 

95 WRIGHT  AIR-SHIP  IN  FLIGHT 187 

96 HOW  THE  WRIGHT  AIR-SHIP  IS  KEPT  AFLOAT 189 

97 THE  SEAT  AND  MOTOR  OF  THE   WRIGHT  AEROPLANE   .      .     .      .  191 

98 THE  BLERIOT  MONOPLANE 192 

ix 


ILLUSTRATIONS 


FIG.  PAGE 

99 — THE  "PLUNGER" 195 

100 U.  S.  SUBMARINE  "  SHARK"  READY  FOR  A  DIVE 197 

101 FIRST  SUBMARINE  CONSTRUCTED  IN  THE  UNITED  STATES.     IT 

WENT  TO   THE   BOTTOM   WITH   SEVEN   MEN,   WHO   WERE 

DROWNED 198 

IO2 HOW    MEN    IN    A    SUBMARINE    SEE    WHEN    UNDER    THE    WATER    .  199 

103 A    TOP    THAT    SPINS    ON    A    STRING 2OO 

104 A    CAR    THAT    RUNS    ON    ONE    RAIL 2O2 

105 MANUFACTURING    DIAMONDS FIRST    OPERATION 207 

106 MANUFACTURING    DIAMONDS SECOND    OPERATION          ....  209 

107 MANUFACTURING    DIAMONDS THIRD    OPERATION 211 

I08 MARCONI     AND     HIS    WIRELESS  -  TELEGRAPH     SENDING    AND     RE- 
CEIVING   INSTRUMENTS .  215 

109 DIAGRAM    OF   WIRELESS-TELEGRAPH    SENDING    APPARATUS       .       .  217 

1 10 DIAGRAM       OF       MARCONI       WIRELESS-TELEGRAPH        RECEIVING 

APPARATUS 2l8 

III RECEIVER  OF  BELL'S  PHOTOPHONE 223 

112 A  GAS  FLAME  IS  SENSITIVE  TO  ELECTRIC  WAVES       ....  224 

113 CAPTAIN     INGERSOLL    ON     BOARD    THE     U.     S.     BATTLE  -  SHIP 

"CONNECTICUT"  USING  THE  WIRELESS  TELEPHONE     .     .  226 
114 INCANDESCENT    ELECTRIC    LAMP    LIGHTED    THOUGH    NOT    CON- 
NECTED TO  ANY  BATTERY  OR  DYNAMO 229 

115 AN  ELECTRIC  DISCHARGE  AT  A  PRESSURE  OF  I2,OOO,OOO  VOLTS, 

A  CURRENT  OF  8OO  AMPERES  IN  THE  SECONDARY  COIL  .      .  230 

Il6 AN  ELECTRIC  DISCHARGE  SIXTY-FIVE  FEET  IN  LENGTH       .     .  231 

117 A  PHYSICIAN  EXAMINING  THE  BONES  OF  THE  ARM  BY  MEANS 

OF    X-RAYS .*......  233 

Il8 X-RAY    PHOTOGRAPH    OF    THE    EYE 234 

119 PHOTOGRAPH     MADE    WITH    RADIUM           235 


INTRODUCTORY   NOTE 

inventions  are  a  never-failing  source  of  interest 
to  all  of  us,  and  particularly  to  the  boy  in  his  teens. 
The  dynamo,  the  electric  motor,  the  telegraph,  with  and 
without  wires,  the  telephone,  air-ships,  and  many  other 
inventions  excite  in  him  an  interest  which  is  deeper  than 
mere  curiosity.  He  wants  to  know  how  these  things  work, 
and  how  they  were  invented.  The  man  is  so  absorbed  in 
the  present  that  he  cares  little  for  the  past.  Not  so  with 
the  boy.  He  cares  for  the  history  of  inventions,  and  in 
this  he  is  wiser  than  the  man,  for  it  is  only  by  a  study  of 
its  origin  and  growth  that  we  can  understand  the  larger 
significance  of  a  great  invention. 

Great  inventions  have  their  origin  in  great  discoveries. 
The  story  of  great  inventions,  therefore,  includes  the  story 
of  the  discoveries  out  of  which  they  have  arisen.  The 
stories  of  the  discoveries  and  the  inventions  are  inseparable 
from  the  lives  of  the  men  who  made  them,  and  so  we  must 
deal  with  biography,  which  in  itself  is  of  interest  to  the 
boy.  Such  a  story  is  the  story  of  physical  science  in  the 
service  of  humanity. 

The  interest  of  the  youth  in  great  inventions  is  unques- 
tioned. Shall  we  stifle  this  interest  by  overemphasis  of 

xi 


INTRODUCTORY    NOTE 


technical  detail,  or  shall  we  minister  to  it  as  a  thing  vital 
in  the  life  of  the  youth  of  to-day  ? 

A  few  sentences  quoted  from  G.  Stanley  Hall  will  indi- 
cate the  author's  point  of  view.  "The  youth  is  in  the 
humanist  stage.  Nature  is  sentiment  before  it  becomes 
idea  or  formula  or  utility."  "The  heroes  and  history 
epochs  of  each  branch  [of  science]  add  another  needed 
quality  to  the  still  so  largely  humanistic  stage."  "A  new 
discovery,  besides  its  technical  record,  involves  the  added 
duty  of  concise  and  lucid  popular  statement  as  a  tribute 
to  youth."  The  need  of  a  "concise  and  lucid  popular 
statement"  of  the  rise  of  the  great  inventions  which 
form  the  material  basis  of  our  modern  civilization  and 
all  of  which  are  new  to  the  young  mind,  has  no  doubt 
been  keenly  felt  by  others  as  it  has  been  by  the  author. 
The  story  of  our  great  inventions  has  been  told  in  sundry 
volumes  for  adult  readers,  but  nowhere  has  this  story,  alive 
with  human  interest,  been  told  in  a  form  suited  to  the 
young.  It  was  the  realization  of  this  need  growing  out  of 
years  of  experience  in  teaching  these  branches  that  led  the 
author  to  attempt  the  task  of  writing  the  story. 

The  purpose  of  this  book  is  to  tell  in  simple  language 
how  our  great  inventions  came  into  being,  to  depict  the  life- 
struggles  of  the  men  who  made  them,  and,  in  the  telling- of 
the  story,  to  explain  the  working  of  the  inventions  in  a 
way  the  boy  can  understand.  The  stories  which  are  here 
woven  together  present  the  great  epochs  in  the  history  of 
physics,  and  are  intended  to  give  to  the  young  reader  a 
connected  view  of  the  way  in  which  our  great  inventions 
have  arisen  out  of  scientific  discovery  on  the  one  hand,  and 

xii 


INTRODUCTORY   NOTE 


conditions  which  we  may  call  social  and  economic  on  the  other 
hand.  If  the  book  shall  appeal  to  young  readers,  and  lead 
them  to  an  appreciation  of  the  meaning  of  a  great  inven- 
tion, the  author  will  feel  that  his  purpose  has  been  achieved. 

The  author  is  deeply  indebted  to  Dr.  Charles  A.  McMurry 
and  Prof.  Newell  D.  Gilbert,  of  the  Northern  Illinois  State 
Normal  School;  Profs.  C.  R.  Mann  and  R.  A.  Millikan,  of 
the  University  of  Chicago;  and  Prof.  John  F.  Woodhull,  of 
Columbia  University,  for  reading  the  manuscript  and  offer- 
ing valuable  suggestions.  Acknowledgment  is  further 
made  here  of  valuable  aid  in  collecting  material  for  illus- 
trations and  letter-press.  Such  acknowledgment  is  due 
to  Prof.  A.  Gray,  University  of  Glasgow;  Prof.  Antonio 
Favaro,  Royal  University  of  Padua;  Prof.  A.  Zammarchi, 
Brescia,  Italy;  Mr.  Nikola  Tesla;  the  Royal  Institution, 
London;  McC lure's  Magazine;  The  Technical  World  Maga- 
zine; The  Scientific  American;  the  Ellsworth  Company; 
Commonwealth-Edison  Company;  Association  of  Edison 
Illuminating  Companies;  Electric  Controller  and  Supply 
Company;  Kelley-Koett  Manufacturing  Company;  Watson- 
Stillman  Company ;  Gould  Storage  Battery  Company ;  Thor- 
darson  Electric  Company ;  the  Westinghouse  Machine  Com- 
pany; Marconi  Wireless  Telegraph  Company  of  America, 
and  the  Siemens-Schuckert  Werke,  Berlin. 

The  drawings  illustrating  Faraday's  experiments  are 
from  exact  reproductions  of  Faraday's  apparatus,  made 
by  Mr.  Joseph  G.  Branch,  author  of  Conversations  on  Elec- 
tricity, and  are  reproduced  by  his  kind  permission. 

E.  E.  B. 

CHICAGO,  June,  1910. 


THE 
STORY  OF  GREAT  INVENTIONS 


THE 
STORY    OF    GREAT    INVENTIONS 

Chapter  I 

THE   AGE    OF    ARCHIMEDES 

Archimedes,  the  First  Great  Inventor 

ARCHIMEDES,  the  first  great  inventor,  lived  in  Syracuse 
/i  more  than  two  thousand  years  ago.  Syracuse  was  a 
Greek  city  on  the  island  of  Sicily.  The  King  of  Syracuse, 
Hiero,  took  great  interest  in  the  discoveries  of  Archimedes. 
One  day  Archimedes  said  to  King  Hiero  that  with  his  own 
strength  he  could  move  any  weight  whatever.  He  even 
said  that,  if  there  were  another  earth  to  which  he  could  go, 
he  could  move  this  earth  wherever  he  pleased.  The  King, 
full  of  wonder,  begged  of  him  to  prove  the  truth  of  his  state- 
ment by  moving  some  very  heavy  weight.  Whereupon 
Archimedes  caused  one  of  the  King's  galleys  to  be  drawn 
ashore.  This  required  many  hands  and  much  labor.  Hav- 
ing manned  the  ship  and  put  on  board  her  usual  loading,  he 
placed  himself  at  a  distance  and  easily  moved  with  his  hand 
the  end  of  a  machine  which  consisted  of  a  variety  of  ropes 

i 


r:  OF    GREAT    INVENTIONS 

and  pulleys,  drawing  the  ship  over  the  sand  in  as  smooth 
and  gentle  a  manner  as  if  she  had  been  under  sail.  The 
King,  quite  astonished,  prevailed  with  Archimedes  to  make 
for  him  all  manner  of  machines  which  could  be  used  either 
for  attack  or  defence  in  a  siege. 

The  Battle  of  Syracuse 

During  the  life  of  King  Hiero  Syracuse  had  no  occasion 
to  use  the  war  machines  of  Archimedes.  The  grandson  of 
King  Hiero,  who  succeeded  to  the  throne,  was  a  tyrant.  He 
attempted  to  throw  off  the  sovereignty  of  Rome  and  en- 
tered into  an  alliance  with  Carthage.  His  cruelty  toward 
his  own  people  was  so  great  that,  after  a  short  reign,  he  was 
assassinated.  There  was  anarchy  in  Syracuse  for  a  time, 
the  Roman  and  anti-Roman  parties  striving  for  supremacy. 
The  anti-Roman  party  gaining  possession  of  the  city,  the 
Romans,  in  order  to  bring  Syracuse  again  into  subjection, 
prepared  for  an  attack  by  sea  and  land.  Then  it  was  that 
Syracuse  had  need  of  the  war  machines  made  by  Archimedes 
(Fig.  i). 

The  Romans  came  with  a  large  land  force  and  a  fleet. 
They  were  sure  that  within  five  days  they  could  conquer  the 
city.  But  there  are  times  when  one  man  with  brains  is 
worth  more  than  an  army.  In  the  battle  which  followed, 
Archimedes  with  his  inventions  was  more  than  a  match  for 
the  Romans. 

The  city  was  strong  from  the  fact  that  the  wall  on  one  side 
lay  along  a  chain  of  hills  with  overhanging  brows ;  on  the 
other  side  the  wall  had  its  foundation  close  down  by  the  sea. 


FIG.     I THE    BATTLE    OF    SYRACUSE 

The  city  defended  by  the  inventions  of  Archimedes. 


THE  STORY  OF  GREAT  INVENTIONS 

A  fleet  of  sixty  ships  commanded  by  Marcellus  bore  down 
upon  the  city.  The  ships  were  full  of  men  armed  with  bows 
and  slings  and  javelins  with  which  to  dislodge  the  men  who 
fought  on  the  battlements.  Eight  ships  had  been  fastened 
together  in  pairs.  These  double  vessels  were  rowed  by  the 
outer  oars  of  each  of  the  pair.  On  each  pair  of  ships  was  a 
ladder  four  feet  wide  and  of  a  height  to  reach  to  the  top  of 
the  wall.  Each  side  of  the  ladder  was  protected  by  a  railing, 
and  a  small  roof-like  covering,  called  a  penthouse,  was  fast- 
ened to  the  upper  end  of  the  ladder.  This  covering  served 
to  protect  the  soldiers  until  they  could  reach  the  top  of  the 
wall.  They  thought  to  bring  these  double  ships  close  to 
shore,  raise  the  ladders  by  ropes  and  pulleys  until  they  rest- 
ed against  the  wall,  then  scale  the  wall  and  capture  the  city. 

But  Archimedes  had  crossbows  ready,  and,  when  the  ships 
were  still  at  some  distance,  he  shot  stones  and  darts  at  the 
enemy,  wounding  and  greatly  annoying  them.  When  these 
began  to  carry  over  their  heads,  he  used  smaller  crossbows  of 
shorter  range,  so  that  stones  and  darts  fell  constantly  in  their 
midst.  By  this  means  he  checked  their  advance,  and  finally 
Marcellus,  in  despair,  was  obliged  to  bring  up  his  ships  under 
cover  of  night.  But  when  they  had  come  close  to  land,  and 
so  too  near  to  be  hit  by  the  crossbows,  they  found  that 
Archimedes  had  another  contrivance  ready.  He  had  pierced 
the  wall  as  high  as  a  man's  head  with  many  loopholes  which 
on  the  outside  were  about  as  big  as  the  palm  of  the  hand. 
Inside  the  wall  he  had  stationed  archers  and  men  with  cross- 
bows to  shoot  down  the  marines.  By  these  means  he  not 
only  baffled  the  enemy,  but  killed  the  greater  number  of 
them.  When  they  tried  to  use  their  ladders,  they  discovered 

4 


THE   AGE   OF   ARCHIMEDES 


that  he  had  cranes  ready  all  along  the  walls,  not  visible  at 
other  times  but  which  suddenly  reared  themselves  above  the 
wall  from  the  inside  and  stretched  their  beams  far  over  the 
battlements,  some  of  them  carrying  stones  weighing  about 
five  hundred  pounds,  and  others  great  masses  of  lead.  So, 
whenever  the  ships  came  near,  these  beams  swung  round  on 
their  pivots  and  by  means  of  a  rope  running  through  a 
pulley  dropped  the  stones  upon  the  ships.  The  result  was 
that  they  not  only  smashed  the  ships  to  pieces,  but  killed 
many  of  the  soldiers  on  board. 

Another  machine  made  by  Archimedes  was  an  "iron 
hand"  or  grappling-hook  swung  on  a  chain  and  carried  by  a 
crane.  The  hook  was  dropped  on  the  prow  of  a  ship,  and 
when  it  had  taken  hold  the  ship  was  lifted  until  it  stood  on 
its  stern,  then  quickly  dropped,  causing  it  either  to  sink  or 
ship  a  great  quantity  of  water. 

With  such  machines,  unknown  before,  Archimedes  drove 
back  the  enemy.  On  the  landward  side  similar  machines 
were  used.  The  Romans  were  reduced  to  such  a  state  of 
terror  that  ' '  if  they  saw  but  a  rope  or  a  stick  put  over  the 
walls  they  cried  out  that  Archimedes  was  levelling  some 
machine  at  them  and  turned  their  backs  and  fled." 

After  a  long  siege,  however,  hunger  forced  the  Syracusans 
to  surrender.  Marcellus  so  admired  the  genius  of  Archi- 
medes that  he  gave  orders  that  he  should  not  be  injured. 
Yet,  in  the  sack  of  the  city  which  followed,  Archimedes  was 
slain  by  a  Roman  soldier. 

The  Roman  historian  Livy  records  that  "Archimedes, 
while  intent  on  some  figures  which  he  had  made  in  the  dust, 
although  the  confusion  was  as  great  as  could  possibly  be, 

5 


THE  STORY  OF  GREAT  INVENTIONS 

was  put  to  death  by  a  soldier  who  did  not  know  who  he  was ; 
that  Marcellus  was  greatly  grieved  at  this,  and  that  pains 
were  taken  about  his  funeral,  while  his  relations  also  were 
carefully  sought  and  received  honor  and  protection  on  ac- 
count of  his  name  and  memory." 

Archimedes*  Principle 

Hiero,  when  he  became  King  of  Syracuse,  decreed  that  a 
crown  of  gold,  of  great  value,  should  be  placed  in  a  certain 
temple  as  an  offering  to  the  gods,  and  sent  to  a  manufacturer 
the  correct  weight  of  gold.  In  due  time  the  crown  was 
brought  to  the  King,  and  a  beautiful  piece  of  work  it  was. 
The  weight  of  the  crown  was  the  same  as  that  of  the  gold, 
but  a  report  was  circulated  that  some  of  the  gold  had  been 
taken  out  and  silver  supplied  in  its  place.  Hiero  was  angry, 
but  knew  no  method  by  which  the  theft  might  be  detected. 
He  therefore  requested  Archimedes  to  give  the  matter  his 
attention. 

While  trying  to  solve  this  problem  Archimedes  went  one 
day  to  a  bath.  As  he  got  into  the  bath-tub  he  saw  that  as 
his  body  became  immersed  the  water  ran  out  of  the  tub. 
He  quickly  saw  how  he  could  solve  the  problem,  leaped  out 
of  the  bath  in  joy,  and,  running  home  naked,  cried  out  with 
a  loud  voice  "Eureka!  eureka!"  (I  have  found  it!  I  have 
found  it!) 

Using  a  piece  of  gold  and  a  piece  of  silver,  each  equal  in 
weight  to  the  crown,  and  a  large  vase  full  of  water,  he 
proved  that  the  crown  was  not  pure  gold,  and  found  how 
much  silver  had  been  mixed  with  the  gold. 

The  incident  of  the  golden  crown  may  have  been  the 

6 


THE   AGE   OF   ARCHIMEDES 

starting-point  of  Archimedes'  study  of  solid  bodies  when 
immersed  in  fluids.  Every  one  knows  that  a  boy  can  lift 
a  heavy  stone  under  water  that  he  could  not  lift  out  of 
water.  The  stone  seems  lighter  when  in  the  water.  A  diver 
with  his  lead-soled  shoes  could  scarcely  walk  on  land,  but 
walks  easily  under  water.  When  the  diver  comes  up,  the 
place  where  he  was  immediately  becomes  filled  with  water. 
Now,  whatever  that  water  weighs  which  fills  the  diver's 
place,  just  that  much  weight  will  the  diver  lose  when  he  goes 
dowrn.  What  is  true  of  the  diver  is  true  of  the  stone  or  of 
any  object  under  water.  The  stone  when  in  the  water  loses 
just  as  much  weight  as  the  weight  of  the  water  that  would 
fill  its  place.  This  is  the  fact  which  was  discovered  by 
Archimedes  and  which  is  called  "Archimedes'  Principle." 

It  is  said  by  an  ancient  author  that  Archimedes  invented 
more  than  forty  machines.  Of  these  the  best  known  are 
the  block  and  tackle,  the  endless  screw  (worm  gear),  and  the 
water  snail,  or  Archimedean  screw.  Yet  his  delight  was  not 
in  his  machines,  but  in  his  mathematics.  Though  he  had 
invented  machines  to  please  his  king,  he  regarded  such  work 
as  trifling,  and  took  little  interest  in  the  common  needs  of 
life. 

Inventions  of  the  Ancient  Greeks 

The  common  needs  of  life  are  to-day  the  chief  concern  of 
the  greatest  men,  and  so  we  find  it  hard  to  sympathize  with 
this  view  of  Archimedes.  His  view,  however,  was  that  of 
other  learned  men  of  his  time,  that  the  common  needs  of 
life  are  beneath  the  dignity  of  the  scholar,  and  so  we  can  see 
why  the  Greeks  made  so  few  great  inventions. 

7 


THE  STORY  OF  GREAT  INVENTIONS 

Hero,  who  lived  a  century  later  than  Archimedes,  invented 
a  steam-engine,  which,  however,  was  only  a  toy.  A  water- 
clock,  in  which  the  first  cog-wheels  were  used,  was  invented 
by  another  Greek  named  Ktesibus,  who  also  invented  the 
force-pump.  The  suction-pump  was  known  in  the  time  of 
Aristotle,  who  lived  about  a  century  before  the  time  of 
Archimedes,  but  the  inventor  is  unknown. 

Concerning  electricity,  the  Greeks  knew  very  little.  They 
knew  that  amber  when  rubbed  will  attract  light  objects, 
such  as  dust  or  chaff.  Amber  was  called  by  the  Greeks 
"electron,"  because  it  reflected  the  brightness  of  the  sun- 
light, and  their  name  for  the  sun  was  "Elector."  From  the 
Greek  name  for  amber  we  get  our  word  "electricity." 

The  Greeks  possessed  scarcely  more  knowledge  of  magnets 
than  of  electricity.  In  fact,  their  ideas  of  magnets  cannot 
be  called  knowledge,  for  they  consisted  chiefly  of  legends. 

They  told  of  the  shepherd  Magnes,  who,  while  watching 
his  flock  on  Mount  Ida,  suddenly  found  the  iron  ferrule  of 
his  staff  and  the  nails  of  his  shoes  adhering  to  a  stone;  that, 
later,  this  stone  was  called,  after  him,  the  "Magnes  stone," 
or  "Magnet." 

They  told  impossible  stories  of  iron  statues  being  sus- 
pended in  the  air  by  means  of  magnets,  and  of  ships  sailing 
near  the  magnetic  mountains  when  every  nail  and  piece  of 
iron  in  the  ship  would  fly  to  the  mountain,  leaving  the  ship 
a  wreck  upon  the  waves. 


Chapter   II 

THE    AGE   OF    GALILEO 

Galileo  and  the  Battle  for  Truth 

FOR  eighteen  centuries  after  the  time  of  Archimedes 
no  inventions  of  importance  were  made.  Men  sought 
for  truth  where  truth  could  not  be  found.  They  looked 
within  their  mouldy  manuscripts  and  asked,  ''What  do  the 
great  philosophers  say  ought  to  happen?"  instead  of  look- 
ing at  nature  and  asking,  "What  does  happen  ?"  And  when 
a  man  arose  who  dared  to  doubt  the  authority  of  the  old 
masters  and  turn  to  nature  to  find  out  the  truth,  all  the 
weapons  at  the  command  of  the  old  school  were  hurled 
against  him. 

Let  us,  at  this  distance,  blame  neither  the  one  side  nor 
the  other.  The  conflict  was  inevitable.  It  was  an  acci- 
dent of  history  that  the  brunt  of  the  attack  fell  upon  a 
man  born  in  Italy  in  1564,  and  that  the  battle  was  fought 
chiefly  in  the  "Eternal  City,"  from  which  centuries  before 
had  marched  the  legions  that  conquered  the  world. 

The  boy,  Galileo,  who  was  to  become  the  central  figure 
of  the  great  conflict,  was  talented  in  many  ways.  In  lute- 
playing  his  skill  excelled  that  of  his  father,  who  was  one  of 
the  noted  musicians  of  his  day.  His  skill  in  drawing  was 

9 


THE  STORY  OF  GREAT  INVENTIONS 

such  that  noted  artists  submitted  their  work  to  him  for 
criticism.  He  wrote  essays  on  the  works  of  Dante  and 
other  classical  writers.  He  amused  his  boy  companions  by 
constructing  toy  machines  which,  though  ingenious,  did  not 
always  work. 

His  preference  was  for  mechanics,  but,  as  this  subject 
offered  little  prospect  of  profitable  work,  he  took  up  the 
study  of  medicine  in  accordance  with  his  father's  wishes. 

In  his  eighteenth  year  he  entered  the  University  of  Pisa. 
Here  he  found  men  who  refused  to  think  for  themselves, 
but  decided  every  question  by  referring  to  what  the  ancient 
philosophers  said.  Galileo  could  not  endure  such  slavish 
submission  to  authority.  So  strongly  did  he  assert  himself 
that  he  was  nicknamed  "The  Wrangler,"  and,  by  his  wrang- 
ling, he  lost  a  scholarship  in  the  university. 

He  neglected  his  medical  studies  and  secretly  studied 
mathematics.  His  father,  learning  of  this,  consented  to  his 
becoming  a  mathematician.  Thus  he  followed  his  bent, 
though  it  seemed  to  lead  directly  to  poverty. 

The  Pendulum  Clock 

It  was  while  a  student  at  the  University  of  Pisa  that 
he  discovered  a  law  of  pendulums  which  makes  possible 
our  pendulum  clocks.  While  at  his  devotions  in  the  cathe- 
dral, he  observed  the  swinging  of  the  bronze  lamp  which 
had  been  drawn  back  for  lighting.  Timing  its  swinging  by 
means  of  his  pulse,  the  only  timepiece  in  his  possession,  he 
found  that  the  time  of  one  swing  remained  the  same,  though 
the  length  of  the  swing  grew  smaller  and  smaller.  This 

10 


FIG.  2 — GALILEO'S  PENDULUM  CLOCK 
It  had  only  one  hand,  which  is  not  shown  in  the  picture. 


THE  STORY  OF  GREAT  INVENTIONS 

discovery  led  to  his  invention  of  an  instrument  for  physi- 
cians' use  in  timing  the  pulse.  About  fifty  years  later  he 
invented  the  pendulum  clock  (Fig.  2). 

Lack  of  funds  compelled  him  to  leave  the  university  with- 
out completing  his  course.  He  returned  to  the  parental 
roof  and  continued  his  scientific  studies.  The  writings  of 
Archimedes  were  his  favorite  study.  With  Archimedes' 
famous  experiment  on  King  Hiero's  crown  as  a  starting- 
point,  he  discovered  the  laws  of  floating  bodies,  which  ex- 
plain why  a  ship  or  other  object  floats  on  water,  and  in- 
vented a  balance  for  weighing  objects  in  water. 

But  such  employment  won  nothing  more  substantial  than 
honor  and  fame.  Food  and  clothing  were  needed.  For 
two  years  he  strove  without  success  to  secure  employment. 
At  the  end  of  that  time  he  was  appointed  professor  of  mathe- 
matics in  the  University  of  Pisa  at  the  magnificent  salary 
of  sixty  scudi  (about  sixty-three  dollars)  per  year.  "But 
any  port  in  a  storm;  and  in  Galileo's  needy  circumstances 
even  this  wretched  salary  was  not  to  be  rejected."  More- 
over, he  could  add  somewhat  to  his  income  by  private 
tutoring. 

Galileo's  Experiment  with  Falling  Shot 

While  teaching  at  the  University  of  Pisa,  he  performed 
his  famous  experiment  of  dropping  from  the  top  of  the 
leaning  tower  two  shot,  one  weighing  ten  pounds,  the  other 
one  pound.  Now,  according  to  Aristotle,  the  ten-pound 
shot  should  fall  in  one-tenth  the  time  required  by  the  one- 
pound  shot.  But  the  assembled  company  of  professors  and 
students  saw  the  two  shot  start  together,  fall  together,  and 

12 


THE    AGE    OF    GALILEO 


strike  the  ground  at  the  same  instant,  and  still  refused  to 
believe  their  own  eyes.  They  continued  to  affirm  that  a 
weight  of  ten  pounds  would  reach  the  ground  in  a  tenth  of 
the  time  taken  by  a  one-pound  weight,  because  they  were 
able  to  quote  chapter  and  verse  in  which  Aristotle  assured 
them  that  such  is  the  fact.  Thus  Galileo  made  enemies  of 
the  other  professors,  but  for  a  time  they  could  do  nothing 
more  than  annoy  him. 

About  this  time  Galileo  incurred  the  wrath  of  the  Grand 
Duke  of  Tuscany,  from  whom  he  had  received  his  appoint- 
ment. He  was  commissioned  to  examine  a  machine  in- 
vented by  a  nephew  of  the  Grand  Duke  for  the  purpose  of 
cleaning  harbors.  Galileo  plainly  said  that  the  machine 
was  worthless.  It  was  tried,  and  his  opinion  proved  true. 
But  like  the  kings  of  olden  time  who  killed  the  bearer  of 
evil  tidings  even  though  the  tidings  were  true,  his  enemies 
made  his  position  so  unpleasant  that  he  resigned. 

He  had  neither  employment  nor  money.  His  father's 
death  occurring  about  this  time,  threw  upon  him  the  care 
of  a  mother,  a  worthless  brother,  and  two  sisters.  In  his 
distress  he  sought  help  from  a  friend,  and  secured  an  ap- 
pointment as  professor  of  mathematics  in  the  University  of 
Padua .  His  salary  was  one  hundred  and  eighty  florins  (about 
ninety-five  dollars),  while  other  professors  received  more 
than  ten  times  as  much. 

While  at  Padua,  Galileo  was  busy  inventing.  He  in- 
vented the  sector,  which  is  to  be  found  in  most  cases  of 
mathematical  instruments  and  is  used  in  certain  kinds  of 
drawing.  He  also  invented  an  air  thermometer  (Fig.  3), 
the  first  instrument  for  measuring  temperature. 

13 


FIG.    3 AN     AIR    THERMOMETER 

When  the  air  in  the  bulb  grows  cooler  it  contracts,  and  the  air  outside 
forces  the  water  up  the  tube.  When  the  air  in  the  bulb  grows  warmer  it 
expands  and  forces  the  water  down  in  the  tube. 


THE    AGE    OF    GALILEO 


In  1604  there  appeared  a  new  star  of  great  brilliancy. 
It  continued  to  shine  with  varying  brightness  for  eighteen 
months,  and  then  vanished.  This  was  a  strange  event,  and 
Galileo  made  use  of  it.  He  proved  that  the  new  star  must 
lie  among  the  most  distant  of  the  heavenly  bodies,  and  this 
fact  did  not  agree  with  Aristotle's  view  that  the  heavens 
are  perfect,  and  therefore  never  change.  A  heated  con- 
troversy followed,  and  Galileo  came  out  boldly  in  favor 
of  the  theory  that  the  earth  revolves  about  the  sun,  the 
prevailing  notion  then  being  that  the  earth  does  not 
move,  but  that^the  sun  and  other  heavenly  bodies  revolve 
around  it. 

The  Telescope 

In  1609  Galileo  learned  of  a  discovery  that  was  to  be  of 
great  value  to  the  world,  but  a  source  of  untold  trouble  to 
himself.  An  apprentice  of  a  Dutch  optician,  while  playing 
with  spectacle  lenses,  chanced  to  observe  that  if  two  of 
the  lenses  were  placed  in  a  certain  position  objects  seen 
through  them  appeared  much  nearer.  Galileo,  learning  of 
this,  set  to  work  to  construct  a  spy  -  glass,  applying  his 
knowledge  of  light.  In  one  day  he  had  constructed  such 
an  instrument,  in  which  he  used  two  lenses  like  the  lenses 
of  the  modern  opera -glass.  Thus,  while  the  Dutchman's 
discovery  was  by  accident,  Galileo's  was  by  reasoning,  and 
was  the  more  fruitful,  as  we  shall  see.  % 

Galileo  continued  improving  his  telescope  until  he  had 

made  one  which  would  magnify  thirty  times.     He  was  the 

first  to  apply  the  telescope  to  the  study  of  the  heavenly 

bodies.     The  most  startling  of  his  discoveries  was  that  of 

2  15 


THE    STORY   OF   GREAT   INVENTIONS 

the   moons   of   the   planet   Jupiter,   which   he   called   new 
planets. 

This  aroused  the  fury  of  his  enemies,  who  ridiculed  the 
idea  of  there  being  new  planets;  "for,"  they  said,  "to  see 
these  planets  they  must  first  be  put  inside  the  telescope." 
The  excitement  was  intense.  Poets  chanted  the  praise  of 
Galileo.  A  public  fete  was  held  in  his  honor.  One  of  his 
pupils  was  imprisoned  in  the  tower  of  San  Marco,  where 
he  had  gone  to  make  observations  with  his  telescope,  and 
could  not  escape  until  the  crowd  had  satisfied  their  curiosity. 
Some  of  the  philosophers  refused  to  look  lest  they  should 
see  and  be  convinced. 

Galileo's  Struggle 

His  enemies  sought  to  steal  from  him  the  honor  of  his 
discoveries.  Some  claimed  to  have  made  the  discoveries 
before  Galileo  did.  Others  claimed  that  his  discoveries 
were  false,  that  their  only  use  was  to  gratify  Galileo's  vanity 
and  thirst  for  gold.  In  these  trying  times  the  friendship  of 
the  great  astronomer  Kepler  warded  off  some  of  the  most 
exasperating  attacks. 

Galileo's  fame  spread  throughout  Europe.  Students  came 
in  great  numbers,  so  that  he  had  little  leisure  left  for  his 
own  studies.  He  therefore  decided  to  leave  Padua,  and 
secured  an  appointment  as  mathematician  and  philosopher 
to  the  Grand  Duke  of  Tuscany.  This  appointment  took 
him  to  Florence.  It  was  here  that  an  incident  occurred 
that  marked  the  beginning  of  a  persecution  which  continued 
to  the  end  of  his  life. 

As  we  read  the  story  of  this  conflict  let  us  remember  that 

16 


THE   AGE   OF   GALILEO 


it  was  not  primarily  a  conflict  between  the  Roman  Catholic 
Church  and  Galileo.  It  was  a  conflict  of  principles.  On 
the  one  side  were  arrayed  those  who  said  that  men  should 
always  believe  as  the  ancient  writers  did;  on  the  other, 
those  who  said  men  should  think  for  themselves.  In  the 
first  party  were  most  of  the  university  professors  and  others 
who  dreaded  the  introduction  of  new  beliefs,  whether  in 
religion  or  science.  In  the  second  party  were  Galileo  and 
a  small  band  of  devoted  followers. 

At  a  dinner  at  the  table  of  the  Grand  Duke  in  Pisa  the 
conversation  turned  on  the  moons  of  Jupiter.  Some  praised 
Galileo.  Others  condemned  him,  saying  that  the  Holy 
Scriptures  were  opposed  to  his  theory  of  the  motion  of  the 
earth.  A  friend  reported  the  incident  to  Galileo,  and  he 
replied  to  the  arguments  of  his  opponents  in  a  letter  which 
was  made  public.  No  doubt  the  sting  of  his  sarcasm  made 
his  enemies  more  bitter.  He  admitted  that  the  Scriptures 
cannot  lie  or  err,  but  this,  he  said,  does  not  hold  good  of 
those  who  attempt  to  explain  the  Scriptures.  In  another 
letter,  he  quoted  with  approval  a  saying  of  Cardinal  Ba- 
ronius,  "The  Holy  Spirit  intended  to  teach  us  in  the  Bible 
how  to  go  to  Heaven,  not  how  the  heavens  go." 

The  first  shot  had  been  fired.  The  battle  was  on,  and 
the  Church,  because  it  possessed  the  most  powerful  weap- 
ons of  attack,  was  used  by  the  combined  forces  to  break 
the  power  of  Galileo's  reasoning.  He  went  to  Rome  to 
make  his  defence,  but  was  commanded  by  the  Holy  Office 
not  to  hold  or  teach  that  the  sun  is  immovable,  and  that 
the  earth  moves  about  the  sun. 

During  another  visit  to  Rome  there  was  shown  to  Galileo 


THE  STORY  OF  GREAT  INVENTIONS 

an  instrument  which,  it  was  said,  would  show  a  flea  as  large 
as  a  cricket.  Galileo  recalled  that  some  years  before  he 
had  so  arranged  a  telescope  that  he  had  seen  flies  which  he 
said  looked  as  big  as  a  lamb,  and  were  covered  all  over  with 
hair.  This  was  the  first  microscope.  Galileo  quickly  im- 
proved the  instrument,  and  soon  his  microscopes  were  in 
great  demand. 

In  violation  of  the  decree  of  the  Church,  to  which  he  had 
submitted,  he  published  his  most  famous  work  in  which 
he  defended  the  theory  that  the  earth  moves  about  the 
sun.  The  book  was  the  outcome  of  his  life-work,  but  the 
Church  believed  it  dangerous.  He  was  summoned  to 
Rome.  Confined  to  a  sick-bed,  he  pleaded  for  delay,  which 
was  granted.  Before  he  recovered,  however,  the  summons 
was  made  imperative.  He  must  go  to  Rome,  or  be  carried 
in  irons.  He  went  in  a  litter,  carried  by  servants  of  the 
Grand  Duke.  In  Rome  he  was  to  appear  before  the  In- 
quisition. There  he  was  treated  with  a  consideration  never 
before  accorded  to  a  prisoner  of  the  Inquisition.  Nor  was 
he  subjected  to  torture,  as  has  been  stated  by  some.  He 
was  found  guilty  of  teaching  the  doctrine  that  the  sun  does 
not  move,  and  that  the  earth  moves  about  the  sun.  He 
was  compelled  to  recant,  and  sentenced  to  the  prison  of 
the  Holy  Office  and,  by  way  of  penance,  to  repeat  once  a 
week  for  three  years  the  seven  penitential  Psalms. 

He  yielded  without  reserve  to  the  decree  of  the  Inquisi- 
tion, renounced  his  "errors  and  heresies,"  and,  with  his 
hand  on  the  Bible,  took  oath  never  again  to  teach  the  for- 
bidden doctrine. 

And  now,  though  a  shattered  old  man  of  seventy-four, 

18 


THE   AGE   OF   GALILEO 


enjoined  to  silence  on  the  chief  results  of  his  life- work, 
nothing  could  quench  his  devotion  to  science.  In  these 
last  years,  he  published  a  new  book  which,  with  his  earlier 
work,  entitles  him  to  be  regarded  as  the  founder  of  the 
science  of  mechanics. 

In  his  study  of  machines  Galileo  found  that  no  machine 
will  do  work  of  itself.  Whenever  a  machine  is  at  work,  a 
man  or  a  horse,  or  some  other  power,  is  at  work  upon  the 
machine.  In  no  case  will  a  machine  do  work  without  re- 
ceiving an  equal  amount  of  work. 

Torricelli  and  the  Barometer 

Galileo  had  a  pump  which  he  found 
would  not  work  when  the  water  was 
thirty-five  feet  below  the  valve.  He 
thought  the  pump  was  injured,  and 
sent  for  the  maker.  The  maker  as- 
sured him  that  no  pump  would  do 
better.  This  led  Torricelli,  one  of 
Galileo's  pupils,  to  the  discovery  of 
the  barometer.  Men  had  said  that 
water  rises  in  a  pump  because  nature 
abhors  a  vacuum.  Torricelli  believed 
that  air-pressure  and  not  nature's 
"horror  of  a  vacuum"  is  the  cause 
of  water  rising  in  a  pump.  He  in- 
vented the  barometer  to  measure  air- 
pressure. 

The  first  barometer  was  a  glass  tube  filled  with  quick- 
silver or  mercury  (Fig.  4).  The  tube  was  closed  at  the 

19 


FIG.    4 TORRICELLI  S 

EXPERIMENT 


THE  STORY  OF  GREAT  INVENTIONS 

upper  end,  and  the  lower  end,  which  was  open,  dipped  in 
a  dish  of  mercury.  He  allowed  the  tube  to  stand,  and  saw 
that  the  height  of  the  mercury  changed.  This  he  believed 
was  because  the  air-pressure  changed.  Wind,  Torricelli 
said,  is  caused  by  a  difference  of  air-pressure,  which  is  due 
to  unequal  heating  of  the  air.  For  this  reason  a  cool  breeze 
blows  from  the  mountain  top  to  the  heated  valley,  or  from 
sea  to  land  on  a  summer  day. 

Otto  Von  Guericke  and  the  Air-Pump 

About  this  time  a  German  burgomaster,  Otto  von  Guericke, 
of  Magdeburg,  was  performing  experiments  on  air-pressure. 
The  Thirty  Years'  War  had  been  raging  for  thirteen  years. 
The  Swedish  King,  Gustavus  Adolphus,  had  landed  in  Ger- 
many, and  was  winning  victory  after  victory  over  the  im- 
perial troops.  Magdeburg  had  entered  into  an  alliance  with 
the  Swedish  King,  by  which  he  was  granted  free  passage 
through  the  city,  while,  on  the  other  hand,  he  promised  pro- 
tection to  the  city. 

The  imperial  army  under  Tilly  and  Pappenheim  laid  siege 
to  the  city.  On  the  one  side  there  was  hope  that  Gustavus 
would  arrive  in  time  to  effect  a  rescue;  on  the  other,  a  de- 
termination to  conquer  before  such  aid  could  arrive.  While 
Gustavus  was  on  his  way  to  the  rescue,  Magdeburg  was 
taken  by  storm,  and  the  most  horrible  scene  of  the  Thirty 
Years'  War  was  enacted.  Tilly  gave  up  the  city  to  plunder, 
and  his  soldiers  without  mercy  killed  men,  women,  and 
children.  In  the  midst  of  the  scene  of  carnage  the  city  was 
set  on  fire,  and  soon  the  horrors  of  fire  were  added  to  the 

20 


THE    AGE    OF   GALILEO 


horrors  of  the  sword.     In  less  than  twelve  hours  twenty 
thousand  people  perished. 

Guericke 's  house  and  family  were  saved,  but  the  suffer- 
ings of  the  city  were  not  yet  ended.  In  five  years  the  enemy 
was  again  before  the  walls,  and  Magdeburg,  then  in  the 
possession  of  the  Swedes,  was  compelled  to  yield  to  the 
combined  Saxon  and  imperial  troops.  Guericke  entered  the 
service  of  Saxony,  and  was  again  made  mayor  of  the  city. 

In  the  midst  of  these  scenes  of  war,  he  found  time  to  con- 
tinue his  studies.  He  made  the  first  air-pump,  and  with  it 
performed  experiments  which  led  to  some  very  important 
results. 

The  experiments  which  Guericke  made  with  his  air-pump 
aroused  the  attention  of  the  princes,  and  especially  Emperor 
Ferdinand.  Guericke  was  called  to  perform  his  experi- 
ments before  the  Emperor.  The  most  striking  of  these 
experiments  he  performed  with  two  hollow  copper  hemi- 
spheres about  a  foot  in  diameter,  fitted  closely  together. 
When  the  air  was  pumped  out,  sixteen  horses  were  barely 
able  to  pull  the  hemispheres  apart,  though,  when  air  was 
admitted,  they  fell  apart  of  their  own  weight. 

Another  experiment  which  astonished  his  audience  was 
performed  with  the  cylinder  of  a  large  pump  (Fig.  5).  A 
rope  was  tied  to  the  piston.  This  rope  was  passed  over  a 
pulley,  and  a  large  number  of  men  applied  their  strength 
to  the  rope  to  hold  the  piston  in  place.  When  the  air  was 
taken  out  of  the  cylinder,  the  piston  was  forced  down  by 
air-pressure,  and  the  men  were  lifted  violently  from  the 
ground.  This  experiment,  as  we  shall  see,  was  of  great  im- 
portance in  the  invention  of  the  steam-engine. 

21 


FIG.   5 — GUERICKE'S  AIR-PUMP 
Men  lifted  from  the  ground  by  air-pressure. 


THE    AGE    OF    GALILEO 


Guericke's  study  of  air-pressure  led  him  to  make  a  water 
barometer  (Fig.  6).  'This  consisted  of  a  glass  tube  about 
thirty  feet  long  dipping  into  a  dish  of  water.  The  tube  was 
filled  with  water,  and  the  top  projected  above  the  roof  of 
the  house.  On  the  water  in  the  tube  he  placed  a  wooden 
image  of  a  man.  In  fair  weather  the  image  would  be  seen 
above  the  housetop.  On  the  approach  of  a  storm  the 
image  would  drop  out  of  sight.  This  led  his  superstitious 
neighbors  to  accuse  him  of  being  in  league  with  Satan. 

The  first  electrical  machine  was  made  by  Guericke.  This 
was  simply  a  globe  of  sulphur  turning  on  a  wooden  axle. 
He  observed  that  when  the  dry  hand  was  held  against  the 
revolving  globe,  the  globe  would  attract  bits  of  paper  and 
other  light  objects. 

Robert  Boyle  and  the  Pressure  of  Air  and  Steam 

Robert  Boyle,  in  England,  improved  the  air-pump  and 
performed  many  new  and  interesting  experiments  with  it. 
One  of  his  experiments  was  to  make  water  boil  by  means 
of  an  air-pump  without  applying  heat.  It  is  now  well 
known  that  water  when  boiling  on  a  high  mountain  is  not 
so  hot  as  when  boiling  down  in  the  valley.  This  is  because 
the  air-pressure  is  less  on  the  mountain  top  than  in  the  val- 
ley. By  using  an  air-pump  to  remove  the  air-pressure,  water 
may  be  made  to  boil  when  it  is  still  quite  cold  to  the  hand. 

Boyle  compared  the  action  of  air  under  pressure  to  a 
steel  spring.  The  ''spring"  of  the  air  is  evident  to  us  in 
the  pneumatic  tire  of  the  bicycle  or  automobile.  Boyle 
found  that  the  more  air  is  compressed  the  greater  is  its 
pressure  or  "spring,'*  and  that  steam  as  it  expands  exerts 

23 


FIG.  6 — GUERICKE'S  WATER  BAROMETER 

In  fair  weather  the  image  appeared  above  the  housetop.  When  a 
storm  was  approaching  the  image  dropped  below  the  roof  into  the 
house, 


THE   AGE   OF   GALILEO 


less  and  less  pressure.     This  is  important  in  the  steam- 
engine. 

Pascal  and  the  Hydraulic  Press 

It  was  Blaise  Pascal,  a  Frenchman,  who  proved  beyond 
the  possibility  of  a  doubt  that  air-pressure  supports  the  mer- 
cury in  a  barometer,  and 
lifts  the  water  in  a  pump 
(Fig.  7).  He  had  two  mer- 
cury barometers  exactly 
alike  set  up  at  the  foot  of 
a  mountain.  The  mercury 
stood  at  the  same  height  in 
each.  Then  one  barometer 
was  left  at  the  foot  of  the 
mountain,  and  the  other 
was  carried  to  the  summit, 
about  three  thousand  feet 
high.  The  mercury  in  the 
second  barometer  then  stood 
more  than  three  inches  low- 
er than  at  first.  As  the 
barometer  was  carried  down 
the  mountain  the  mercury 
slowly  rose  until,  at  the 
foot,  it  stood  at  the  same 
height  as  at  first.  The  par-  FIG.  7— A  LIFT-PUMP 

-,      !         ,    -i     ir  Air  pressing  down  on  the  water  in 

ty  stopped  about  half-way  the  wjj  cause*  the  water  to  rise  in  the 

down  the   mountain,  allow-    pump.     The  air  can  do  this  only  when 

incr    the  barometer    to  rest   the  PlunSer  is  at  work  removing  air  or 

J   water  and  reducing  the  pressure  inside 

there   for   some   time,   and  the  pump. 

25 


THE  STORY  OF  GREAT  INVENTIONS 


observing  it  carefully.  They  found  that  the  mercury  stood 
about  an  inch  and  a  half  higher  than  at  the  foot  of  the  moun- 
tain. During  all  this  time  the  height  of  the  mercury  in  the 
barometer  which  had  been  left  at  the  foot  of  the  mountain 
did  not  change. 

It  is  now  known  that  when  a  barometer  is  carried  up  to 
a  height  of  nine  hundred  feet,  the  mercury  stands  an  inch 
lower  than  at  the  earth's  surface.  For  every  nine  hundred 
feet  of  elevation  the  mercury  is  lowered  about  one  inch. 
In  this  way  the  height  of  a  mountain  can  be  measured,  and 
a  man  in  a  balloon  or  an  air-ship  can  tell  at  what  height  he 
is  sailing.  For  this  purpose,  however,  a  barometer  is  used 
that  is  more  easily  carried  than  a  mercury  barometer. 

Pascal  invented  the  hy- 
draulic press,  a  machine 
with  which  he  said  he  could 
multiply  pressure  to  any 
extent,  which  reminds  us 
of  Archimedes'  saying  that, 
with  his  own  hand,  he  could 
move  the  earth  if  only  he 
had  a  place  to  stand.  Pas- 
cal could  so  arrange  his 


lib 


FIG.    8 A    SIMPLE    HYDRAULIC    PRESS 

A  one -pound  weight  holds  up  a 
hundred  pounds. 


machine  that  a  man  press- 
ing with  a  force  of  a  hun- 
dred pounds  on  the  handle 

could  produce  a  pressure  of  many  tons.  In  fact,  a  man  can 
so  arrange  this  machine  that  he  can  lift  any  weight  what- 
ever (Fig.  8). 

The  hydraulic  press  has  two  cylinders.     One  cylinder 

26 


THE   AGE   OF   GALILEO 


must  be  larger  than  the  other.  The  two  cylinders  are  filled 
with  a  liquid,  as  water  or  oil,  and  are  connected  by  a  tube 
so  that  the  liquid  can  flow  from  one  cylinder  into  the  other. 
There  is  a  tightly  fitting  piston  in  each  cylinder.  If  one 
piston  has  an  area  of  one  square  inch,  and  the  other  has  an 
area  of  one  hundred  square  inches,  then  every  pound  of 
pressure  on  the  small  piston  causes  a  hundred  pounds  of 
pressure  on  the  large  piston.  A  hundred  pounds  on  the 
small  piston  would  lift  a  weight  of  ten  thousand  pounds  on 
the  large  piston.  But  we  can  see  that  the  large  piston  can- 
not move  as  fast  as  the  small  one  does.  Though  we  can 
lift  a  very  heavy  weight  with  this  machine,  we  must  ex- 
pect this  heavy  weight  to  move  slowly.  There  must  be  a 
loss  in  speed  to  make  up  for  the  gain  in  the  weight  lifted 
(Fig.  9).  An  hydraulic  press  with  belt -driven  pump  is 
illustrated  in  Fig.  10. 

Newton 

Sir  Isaac  Newton  as  a  boy  did  not  show  any  unusual 
talent.  In  school  he  was  backward  and  inattentive  for  a 
number  of  years,  until  one  day  the  boy  above  him  in  class 
gave  him  a  kick  in  the  stomach.  This  roused  him  and,  to 
avenge  the  insult,  he  applied  himself  to  study  and  quickly 
passed  above  his  offending  classmate.  His  strong  spirit 
was  aroused,  and  he  soon  took  up  his  position  at  the  head 
of  his  class. 

It  was  his  delight  to  invent  amusements  for  his  class- 
mates. He  made  paper  kites,  and  carefully  thought  out 
the  best  shape  for  a  kite  and  the  number  of  points  to  which 
to  attach  the  string.  He  would  attach  paper  lanterns  to 

27 


THE  STORY  OF  GREAT  INVENTIONS 


FIG.    9 HOW    AN    HYDRAULIC    PRESS    WORKS 

One  man  with  the  machine  can  exert  as  much  pressure  as  a  hundred 
men  could  without  the  machine.  The  arrows  show  the  direction  in 
which  the  liquid  is  forced  by  the  action  of  the  plunger  p.  The  large 
piston  P  is  forced  up,  thus  compressing  the  paper. 

these  kites  and  fly  them  on  dark  nights,  to  the  delight  of 
his  companions  and  the  dismay  of  the  superstitious  country 
people,  who  mistook  them  for  comets  portending  some  great 
calamity.  He  made  a  toy  mill  to  be  run  by  a  mouse,  which 
he  called  the  miller;  a  mechanical  carriage,  run  by  a  handle 

28 


THE   AGE   OF   GALILEO 


worked  by  the  person  inside,  a  water-clock,  the  hand  of 
which  was  turned  by  a  piece  of  wood  which  fell  or  rose  by 
the  action  of  dropping  water. 

At  the  age  of  fifteen,  his  mother,  then  a  widow,  removed 
him  from  school  to  take  charge  of  the  family  estate.  But 
the  farm  was  not  to  his  liking.  The  sheep  went  astray, 


FIG.     IO AN    HYDRAULIC    PRESS    WITH    BELT-DRIVEN 

PUMP 

29 


THE  STORY  OF  GREAT  INVENTIONS 

and  the  cattle  trod  down  the  corn  while  he  was  perusing 
a  book  or  working  with  some  machine  of  his  own  con- 
struction. His  mother  wisely  permitted  him  to  return  to 
school.  After  completing  the  course  in  the  village  school 
he  entered  Trinity  College,  Cambridge. 


Gravitation 

It  was  in  the  year  following  his  graduation  from  Cam- 
bridge that  he  made  his  greatest  discovery — that  of  the  law 
of  gravitation.  A  plague  had  broken  out  in  Cambridge, 
to  escape  which  Newton  had  retired  to  his  estate  at  Wools- 
thorpe.  Here  he  was  sitting  one  day  alone  in  the  garden 
thinking  of  the  wonderful  power  which  causes  all  bodies  to 
fall  toward  the  earth.  The  same  power,  he  thought,  which 
causes  an  apple  to  fall  to  the  ground  causes  bodies  to  fall 
on  the  tops  of  the  highest  mountains  and  in  the  deepest 
mines.  May  it  not  extend  farther  than  the  tops  of  the 
mountains?  May  it  not  extend  even  as  far  as  the  moon? 
And,  if  it  does,  is  not  this  power  alone  able  to  hold  the 
moon  in  its  orbit,  as  it  bends  into  a  curve  a  stone  thrown 
from  the  hand? 

There  followed  a  long  calculation  requiring  years  to  com- 
plete. Seeing  that  the  results  were  likely  to  prove  his 
theory  of  gravitation,  he  was  so  overcome  that  he  could 
not  finish  the  work.  When  this  was  done  by  one  of  his 
friends,  it  was  found  that  Newton's  thought  was  correct — 
that  the  force  of  gravitation  which  causes  bodies  to  fall  .at 
the  earth's  surface  is  the  same  as  the  force  which  holds  the 
moon  in  its  orbit.  As  the  earth  and  moon  attract  each 


THE    AGE   OF   GALILEO 


other,  so  every  star  and  planet  attracts  every  other  star 
and  planet,  and  this  attraction  is  gravitation. 

Colors  in  Sunlight 

About  the  same  time  that  he  made  his  first  discoveries 
regarding  gravitation,  he  took  up  the  study  of  light  with  a 
view  to  improving  the  construction  of  telescopes.  His  first 
experiment  was  to  admit  sunlight  into  a  darkened  room 
through  a  circular  hole  in  the  shutter,  and  allow  this  beam 
of  light  to  pass  through  a  glass  prism  to  a  white  screen  be- 
yond. He  expected  to  see  a  round  spot  of  light,  but  to 
his  surprise  the  light  was  drawn  out  into  a  band  of  brilliant 
colors. 

He  found  that  the  light  which  comes  from  the  sun  is  not 
a  simple  thing,  but  is  composed  of  colors,  and  these  colors 
were  separated  by  the  glass  prism.  In  the  same  way  the 
colors  of  sunlight  are  separated  by  raindrops  to  form  a  rain- 
bow. The  colors  may  be  again  mingled  together  by  passing 
them  through  a  second  prism.  They  will  then  form  a  white 
light. 

Suppose  that  the  light  of  the  sun  were  not  composed  of 
different  colors,  that  all  parts  of  white  light  were  alike, 
then  there  would  be  no  colors  in  nature.  All  the  trees  and 
flowers  would  have  a  dull,  leaden  hue,  and  the  human 
countenance  would  have  the  appearance  of  a  pencil-sketch 
or  a  photographic  picture.  The  rainbow  itself  would 
dwindle  into  a  narrow  arch  of  white  light;  the  sun  would 
shine  through  a  gray  sky,  and  the  beauty  of  the  setting 
sun  would  be  replaced  by  the  gray  of  twilight  (Fig.  n). 

3  31 


THE  STORY  OF  GREAT  INVENTIONS 


FIG.   ii — NEWTON'S  EXPERIMENT  WITH  THE  PRISM 

Sunlight  separated  into  the  colors  of  the  rainbow.  The  seven  colors 
are:  violet,  indigo,  blue,  green,  yellow,  orange,  red. 

One  of  Newton's  inventions  was  a  reflecting  telescope — 
that  is,  a  telescope  in  which  a  curved  mirror  was  used  in 
place  of  a  lens.  He  made  such  a  telescope  only  six  inches 
long,  which  would  magnify  forty  times. 

Newton  was  a  member  of  the  Convention  Parliament, 
which  declared  James  II.  to  be  no  longer  King  of  England 
and  tendered  the  crown  to  William  and  Mary.  He  was 
made  a  knight  by  Queen  Anne  in  1705. 

His  knowledge  of  chemistry  was  used  in  the  service  of 
his  country  when  he  was  Master  of  the  Mint.  It  was  his 
duty  to  superintend  the  recoining  of  the  money  of  England, 
which  had  been  debased  by  dishonest  officials  at  the  mint. 
He  did  his  work  without  fear  or  favor. 

Once  a  bribe  of  £6000  ($30,000)  was  offered  him.  He 

32 


THE   AGE   OF   GALILEO 


refused  it,  whereupon  the  agent  who  made  the  offer  said  to 
him  that  it  came  from  a  great  duchess.  Newton  replied: 
"  Tell  the  lady  that  if  she  were  here  herself,  and  had  made 
me  this  offer,  I  would  have  desired  her  to  go  out  of  my 
house;  and  so  I  desire  you,  or  you  shall  be  turned  out." 

Although  Newton's  discoveries  in  the  world  of  thought 
were  among  the  greatest  ever  made  by  man,  he  regarded 
them  as  insignificant  compared  with  the  truth  yet  undis- 
covered. He  said  of  himself:  "I  do  not  know  what  I  may 
appear  to  the  world,  but  to  myself  I  seem  to  have  been 
only  like  a  boy  playing  on  the  sea-shore  and  diverting 
myself  in  now  and  then  finding  a  smoother  pebble  or  a 
prettier  shell  than  the  ordinary,  whilst  the  great  ocean  of 
truth  lay  all  undiscovered  before  me." 


Chapter  III 

THE  EIGHTEENTH  CENTURY 

James  Watt  and  the  Steam-Engine 

IF  you  had  visited  the  coal-mines  of  England  and  Scot- 
land three  hundred  years  ago,  you  might  have  seen 
women  bending  under  baskets  of  coal  toiling  up  spiral 
stairways  leading  from  the  depths  of  the  mines.  At  some 
of  the  mines  horses  were  used.  A  combination  of  windlass 
and  pulleys  made  it  possible  for  a  horse  to  lift  a  heavy 
bucket  of  coal.  There  came  a  time,  however,  when  slow 
and  crude  methods  such  as  these  could  not  supply  the  coal 
as  fast  as  it  was  needed.  The  shallower  mines  were  being 
exhausted.  The  mines  must  be  dug  deeper.  The  demand 
for  coal  was  increasing.  The  supply  of  coal,  it  was  thought, 
would  not  last  until  the  end  of  the  century.  The  wood 
supply  was  already  exhausted.  It  seemed  that  England 
was  facing  a  fuel  famine. 

There  was  only  one  way  out  of  the  difficulty.  A  machine 
must  be  invented  that  would  do  the  work  of  the  women 
and  horses,  a  machine  strong  enough  to  raise  coal  with 
speed  from  the  deepest  mines.  Then  it  happened  that  two 
great  inventors,  Newcomen  and  Watt,  arose  to  produce  the 
machine  that  was  needed.  When  the  world  needs  an  in- 

34 


THE   EIGHTEENTH   CENTURY 

vention  it  seldom  fails  to  appear.  It  is  true  of  the  world, 
as  of  an  individual,  that  "Necessity  is  the  mother  of  in- 
vention." 

In  the  mean  time  Torricelli  had  performed  his  famous 
barometer  experiment,  and  Otto  von  Guericke  had  aston- 
ished princes  with  proofs  of  the  pressure  of  the  air.  There 
was  no  apparent  connection  between  these  experiments 
and  the  art  of  coal-mining,  yet  these  discoveries  made  pos- 
sible the  steam-engine  which  was  to  revolutionize  first  the 
coal-mining  industry  and,  later,  the  entire  industrial  world. 

The  First  Steam-Engine  with  a  Piston 

The  first  steam-engine  with  a  piston  was  made  by  Denys 
Papin,  a  Frenchman.  Papin  had  observed  that,  in  Guer- 
icke 's  experiment,  air-pressure  lifted  several  men  off  their 
feet.  So  he  thought  the  air  could  be  made  to  lift  heavy 
weights  and  do  useful  work.  But  how  should  he  produce 
the  vacuum  ?  His  first  thought  was  to  explode  gunpowder 
beneath  the  piston.  The  gunpowder  engine  had  been  tried 
by  others  and  found  wanting.  He  next  turned  his  atten- 
tion to  steam,  and  discovered  that  if  the  piston  were  forced 
up  by  steam  and  then  the  steam  condensed,  a  vacuum  was 
formed  beneath  the  piston,  and  air-pressure  forced  the  pis-- 
ton to  descend.  If  the  piston  were  attached  to  a  weight 
by  a  rope  passing  over  a  pulley,  then,  as  the  piston  de- 
scended, it  would  lift  the  weight.  Papin' s  engine  consisted 
simply  of  a  cylinder  and  piston  (Fig.  12).  There  was  no 
boiler,  but  the  water  was  placed  in  the  cylinder  beneath 
the  piston.  A  fire  was  placed  under  the  cylinder  and,  as 

35 


THE  STORY  OF  GREAT  INVENTIONS 


the  water  boiled,  the  steam  raised  the  piston.  Then  the 
fire  was  removed  and,  as  the  cylinder  cooled,  the  steam 
condensed,  and  the  piston  was  forced  down  by  air-pressure. 

This  was  a  slow  and  awk- 
ward method.  The  engine 
required  several  minutes  to 
make  one  stroke. 

The  principle  of  Papin's 
engine  was  first  success- 
fully applied  by  Thomas 
Newcomen.  Newcomenwas 
a  blacksmith  by  trade,  and 
his  great  successor,  Watt, 
was  a  mechanic.  Thus  we 
see  that  great  discoveries 
soon  become  common  prop- 
erty. The  blacksmith  and 
the  mechanic  soon  learn  to 
use  the  discoveries  of  the 
scientist. 


Newcomen's  Engine 


FIG.    12 PAPIN  S    ENGINE 


In  the  Newcomen  engine 
The  first  steam-engine  with  a  pistori.     the   piston  moved  a  Walk- 
When  the  piston  B  was  forced  down 

by  air-pressure,  a  weight  was  lifted  mg-beam  to  which  Was  at- 
by  means  of  a  rope  TT  passing  over  tacheda  pump-rod.  Steam 
pulleys.  1  ! 

was  used  merely  to  bal- 
ance the  air-pressure  on  the  piston  and  allow  the  pump- 
rod  to  descend  by  its  own  weight.  The  steam  was  con- 

36 


THE   EIGHTEENTH   CENTURY 

densed  in  the  cylinder,  and  the  pressure  of  the  air  forced 
the  piston  down.  Thus  the  work  of  raising  water  in 
the  pump  was  done  by  the  air.  Newcomen's  first  engine 
made  twelve  strokes  a  minute,  and  at  each  stroke  lifted 
fifty  gallons  of  water  fifty  yards.  He  used  this  engine  in 
pumping  water  from  the  mines,  and  also  made  engines  for 
lifting  coal. 

At  first  the  steam  was  condensed  by  throwing  cold  water 
on  the  outside  of  the  cylinder.  But  one  day  the  engine 
suddenly  increased  its  speed  and  continued  to  work  with 
unusual  rapidity.  The  upper  side  of  the  piston  was  cov- 
ered with  water  to  make  the  piston  air-tight,  and  it  was 
found  that  this  water  was  entering  the  cylinder  through 
a  hole  that  had  worn  in  the  piston,  and  this  jet  of  cold 
water  was  rapidly  condensing  the  steam.  This  was  the 
origin  of  ''jet  condensation." 

After  this  steam  and  water  were  alternately  admitted  to 
the  cylinder  through  cocks  turned  by  hand.  A  boy,  Hum- 
phrey Potter,  to  whom  this  work  was  intrusted,  won  fame 
by  tying  strings  to  the  cocks  in  such  a  way  that  the  engine 
would  turn  the  cocks  itself  and  the  boy,  Humphrey,  was 
free  to  play.  This  device  was  the  origin  of  valve-gear.1 

Newcomen's  engine  was  extensively  used.  The  tin  and 
copper  mines  of  Cornwall  were  deepened.  Coal-mines  were 
sunk  to  twice  the  depth  that  had  been  possible.  But  as 

1  Any  device  by  which  a  steam-engine  operates  the  valves  which  admit 
steam  to  the  cylinder  is  called  "  valve-gear."  One  form  of  valve-gear  is 
the  link  motion  invented  by  Stephenson.  This  form  will  be  described 
in  connection  with  the  locomotive.  A  simple  valve-rod,  worked  by  an 
eccentric  such  as  is  used  on  most  stationary  engines,  is  also  a  form  of  valve- 
gear. 

37 


THE  STORY  OF  GREAT  INVENTIONS 

the  mines  were  deepened  the  cost  of  running  the  engines 
increased.  The  largest  engines  consumed  about  $15,000 
worth  of  coal  per  year.  The  Newcomen  engine  required 
about  twenty-eight  pounds  of  coal  per  hour  per  horse-power, 
while  a  modern  engine  consumes  less  than  two  pounds. 
Again,  because  of  increased  cost,  mines  were  being  aban- 
doned. Such  was  the  situation  when  James  Watt  came 
into  the  field  of  action. 

Watt  had  learned  the  mechanic's  trade  in  one  year  in  a 
London  shop,  and,  because  he  had  not  passed  through  an 
apprenticeship  of  seven  years,  the  Guild  of  Hammermen,  a 
labor- union  of  his  time,  refused  him  admission,  and  this 
refusal  meant  no  employment.  He  found  shelter,  however, 
in  the  University  of  Glasgow,  and  was  there  provided  with 
a  small  workshop  where  he  could  make  instruments  for 
sale. 

Watt's  Engine 

A  small  Newcomen  engine  belonging  to  the  University  of 
Glasgow  was  out  of  repair.  London  mechanics  had  failed 
to  make  it  work.  The  job  was  given  to  Watt.  That  he 
might  do  a  perfect  piece  of  work  on  this  engine,  he  made 
a  study  of  all  that  was  then  known  relating  to  steam 
(Fig.  13). 

He  saw  that  there  was  a  great  loss  of  heat  in  admitting 
cold  water  into  the  cylinder  to  condense  the  steam,  and 
that,  to  prevent  this  loss,  the  cylinder  must  be  kept  always 
as  hot  as  the  steam  that  enters  it.  While  thinking  upon 
this  problem  the  idea  came  to  him  that,  if  connection  were 
made  between  the  cylinder  and  a  tank  from  which  the  air 

38 


FIG.  13 THE  NEWCOMEN  ENGINE,  IN  REPAIRING  WHICH 

WATT    WAS    LED    TO    HIS    GREAT    DISCOVERIES 

Preserved  in  the  University  of  Glasgow. 


THE  STORY  OF  GREAT  INVENTIONS 

had  been  pumped  out,  the  steam  would  rush  into  the  tank, 
and  might  there  be  condensed  without  cooling  the  cylinder. 
This  was  the  origin  of  the  condenser. 

We  have  seen  that,  in  the  Newcomen  engine,  the  steam 
acted  only  on  the  under  side  of  the  piston,  air  acting  on 
the  upper  side.  It  occurred  to  Watt  that  the  steam  should 
act  on  both  sides  of  the  piston.  So  he  proposed  to  put  an 
air-tight  cover  on  the  cylinder  with  a  hole  and  stuffing-box 
for  the  piston  to  slide  through  and  to  admit  steam  to  act 
upon  it  instead  of  air.  Thus  he  was  led  to  invent  the  double- 
acting  engine.  The  action  in  the  cylinder  of  Watt's  engine 
was  the  same  as  that  of  the  modern  engine. 

To  save  the  power  of  steam,  Watt  arranged  the  valve  in 
his  engine  in  such  a  way  that  the  steam  was  cut  off  from 
the  cylinder  when  the  piston  had  made  about  one-fourth 
of  a  stroke.  The  steam  in  the  cylinder  continues  to  ex- 
pand and  drive  the  piston.  This  device  more  than  doubles 
the  amount  of  work  that  the  steam  will  do  (Fig.  14). 

Horse-Power  of  an  Engine 

When  horses  were  about  to  be  replaced  by  the  steam- 
engine  at  the  mines,  the  question  was  asked:  "How  many 
horses  will  the  engine  replace  ?"  Tests  were  made  by  Watt 
and  others  before  him  of  the  rate  at  which  a  horse  could 
work  in  pumping  water  or  in  lifting  a  weight  by  means  of 
a  pulley.  Watt's  experiments  showed  that  "a  good  Lon- 
don horse  could  go  on  lifting  150  pounds  over  a  pulley  at 
the  rate  of  2|  miles  an  hour  or  220  feet  per  minute,  and 
continue  the  work  eight  hours  a  day."  This  would  be 

40 


THE   EIGHTEENTH   CENTURY 

equal  to  lifting  33,000  pounds  one  foot  high  every  minute. 
This  rate  of  doing  work  he  called  a  horse-power.  It  is  more 
than  the  average  horse  can  do,  but  this  number  was  used  by 
Watt  that  he  might  give  good  measure  in  his  engines.  The 
horse-power  of  an  engine  at  that  time  meant  the  rate  of 


SLIDE    VALVE 


FIG.   14 CYLINDER   OF    WATT'S    STEAM-ENGINE 

Arrows  show  the  course  of  the  steam. 

work  in  lifting  water  or  coal.  Now  it  means  the  rate  of 
work  done  by  the  steam  upon  the  piston,  so  that  to  find 
the  useful  horse-power  of  an  engine  we  must  deduct  the 
work  wasted  in  friction. 

The  indicator  for  measuring  the  pressure  of  steam  in  the 
cylinder  and  the  fly-ball  governor  are  also  inventions  made 

41 


THE  STORY  OF  GREAT  INVENTIONS 

by  Watt  (Fig.  1 5) .  The  fly -ball  governor  replaced  the  throt- 
tle-valve which  was  at  first  used  by  Watt  to  regulate  the  speed 
of  his  engines.  The  throttle- valve  is  still  used  on  locomotives. 
At  the  end  of  the  eighteenth  century  the  steam-engine 
was  full  grown.  It  remained  for  the  nineteenth  century  to 
apply  the  engine  to  locomotion  on  sea  and  land,  to  develop 
the  steam-turbine,  and  so  to  increase  the  power  of  the 


FIG.    15 A    FLY-BALL    GOVERNOR 

The  balls  as  they  rotate  regulate  the  admission  of  steam 
to  the  cylinder  by  means  of  the  lever  L  and  the  rod  R. 

steam-engine  that,  early  in  the  twentieth  century,  a  68,000- 
horse-power  engine  should  speed  an  ocean  liner  across  the 
Atlantic  in  five  days. 

42 


THE   EIGHTEENTH   CENTURY 


The  Leydcn  Jar 

The  first  electrical  invention  of  practical  use  was  made 
by  Benjamin  Franklin.  In  Franklin's  time  great  interest 
in  electricity  had  been  aroused  by  the  strange  discovery 
of  a  German  professor,  Pieter  van  Musschenbroek,  of  the 
University  of  Ley  den.  This  professor  had  tried  what  he 
called  a  new  but  terrible  experiment.  He  had  suspended 
by  two  silk  threads  a  gun-barrel  which  received  electricity 
from  an  electrical  machine.  From  one  end  of  the  gun-barrel 
hung  a  brass  wire.  The 
lower  end  of  this  wire  dip- 
ped in  a  jar  of  water.  He 
held  the  jar  in  one  hand, 
while  with  the  other  he 
tried  to  draw  sparks  from 
the  gun -barrel.  Suddenly 
he  received  a  shock  which 
seemed  to  him  like  a  light- 
ning stroke.  So  violent  was 
the  shock  that  he  thought 
for  a  moment  it  would  end 
his  life. 

Out  of  this  experiment  came  the  Leyden  jar,  which  for  a 
century  and  a  half  was  of  no  practical  use,  but  which  now 
forms  an  important  part  of  every  wireless  telegraph  equip- 
ment. The  Leyden  jar  is  simply  a  glass  bottle  or  jar  coated 
with  tin-foil  both  inside  and  outside  (Fig.  16).  When 
charged  with  electricity  the  jar  will  hold  its  charge  until 
the  two  coatings  are  connected  by  a  metal  wire  or  other 

43 


FIG.     l6 A    LEYDEN    JAR 


THE  STORY  OF  GREAT  INVENTIONS 

good  conductor  of  electricity.  A  person  may  receive  a  strong 
shock  by  holding  the  jar  in  one  hand  and  touching  a  knob 
connected  to  the  inner  coating  with  the  other  hand. 

Popular  interest  in  electricity  was  aroused  by  this  dis- 
covery. The  friction  electrical  machine  and  the  Ley  den 
jar  were  simple  and  easy  to  make.  People  of  fashion  found 
them  interesting  and  amusing,  the  more  so  because  of  the 
shock  felt  on  taking  through  the  body  the  discharge  from 
the  "wonderful  bottle,"  and  the  fact  that  several  persons 
could  receive  the  shock  at  the  same  instant.  On  one 
occasion  the  Abbe  Nollet  discharged  a  Leyden  jar  through 
a  line  composed  of  all  the  monks  of  the  Carthusian  Monastery 
in  Paris.  As  the  line  of  serious-faced  monks  a  mile  in  length 
jumped  into  the  air,  the  effect  was  ridiculous  in  the  extreme. 

Conductors  and  Insulators 

About  this  time  other  great  electrical  discoveries  were 
made.  Early  in  the  century,  Stephen  Gray  discovered 
that  some  objects  conduct  electricity  and  others  do  not. 
He  discovered  that,  when  a  glass  tube  is  electrified  by 
rubbing,  it  will  attract  and  repel  light  objects.  In  the  same 
way  a  comb  or  penholder  of  rubber  may  be  electrified 
by  rubbing  it  on  the  sleeve.  A  bit  of  paper  which  touches 
the  comb  becomes  electrified.  Electricity  can  be  trans- 
ferred from  one  object  to  another.  Gray  discovered  further 
that  contact  is  not  necessary,  that  a  hempen  thread  or  a 
wire  will  carry  an  electric  charge  from  one  object  to  an- 
other. A  silk  thread  will  not  carry  the  electric  charge. 
"Some  things  convey  electricity,"  he  said,  "and  some  do 

44 


THE   EIGHTEENTH   CENTURY 

not,  and  those  which  do  not  can  be  used  to  prevent  the 
electricity  escaping  from  those  which  do."  Could  this  ob- 
scure inventor  have  seen  a  modern  telegraph  line  with  the 
glass  insulators  on  the  poles,  which  prevent  the  electric 
current  escaping  from  the  telegraph  wire,  he  might  have 
realized  the  importance  of  his  discovery.  He  set  up  a  line 
of  hempen  thread  six  hundred  and  fifty  feet  long,  and  with 
an  electrical  machine  at  one  end  of  the  line  electrified  a 
boy  suspended  from  the  other  end. 

Two  Kinds  of  Electric  Charge 

A  Frenchman,  DuFay,  while  carrying  further  the  experi- 
ments of  Gray,  was  watching  a  bit  of  gold-leaf  floating  in  the 
air.  The  gold-leaf  had  been  repelled  after  contact  with 
his  electrified  glass  tube.  Thinking  to  try  the  act  ion  of 
two  electrified  objects  on  the  gold  leaf,  he  rubbed  a  piece  of 
gum-copal  and  brought  it  near  the  leaf.  To  his  astonish- 
ment the  leaf,  which  was  repelled  by  the  glass  tube,  was 
attracted  by  the  gum-copal.  He  repeated  the  experiment 
again  and  again,  and  each  time  the  leaf  was  repehed  by  the 
glass  and  attracted  by  the  gum.  He  concluded  from  this 
that  there  are  two  kinds  of  electricity,  which  he  named 
"vitreous"  and  "resinous."  The  two  kinds  of  electric 
charge  were  called  by  Franklin  "positive"  and  "negative." 

Franklin  made  a  battery  of  Ley  den  jars,  connecting  the 
inner  coating  of  one  to  the  outer  coating  of  the  next  through- 
out the  series.  In  this  way  he  could  get  a  much  stronger 
spark  than  with  a  single  jar.  On  one  occasion  he  nearly  lost 
his  life  by  taking  a  shock  from  his  battery  of  Ley  den  jars. 

45 


THE  STORY  OF  GREAT  INVENTIONS 

He  magnetized  and  demagnetized  steel  needles  by  passing 
the  discharge  from  his  Leyden  jars  through  the  needles. 


Franklin's  Kite  Experiment 

The  conjecture  that  lightning  is  of  the  same  nature  as  the 
spark  from  the  Leyden  jar  or  the  electrical  machine  had 
gained  a  hold  on  the  minds  of  others  before  Franklin.  In 
France  sparks  had  been  drawn  from  a  rod  ninety-nine  feet 
high,  but  this  did  not  reach  into  the  clouds.  Franklin  de- 
termined to  send  a  kite  into  a  thunder-cloud,  thinking  elec- 
tricity from  the  cloud  would  follow  the  string  of  the  kite 
and  could  be  stored  in  a  Leyden  jar,  and  used  like  the  charge 
from  an  electrical  machine.  He  had  felt  the  power  of  a 
Ley  den- jar  discharge,  and  through  it  had  nearly  lost  his 
life.  He  knew  that  lightning  is  far  more  powerful  than  any 
battery  of  Leyden  jars,  and  yet  to  test  the  truth  of  his 
theory,  that  lightning  is  an  electrical  discharge,  he  was 
about  to  draw  the  lightning  to  his  hand.  He  knew  little  of 
conductors  of  electricity.  Whether  the  cord  would  draw 
little  or  much  of  the  "electric  fire"  he  knew  not.  So  far  as 
he  knew  he  was  toying  with  death. 

The  kite  was  made  of  two  light  strips  of  cedar  placed 
crosswise,  and  a  large  silk  handkerchief  fastened  to  the 
strips.  A  sharp  wire  about  a  foot  long  was  fastened  to 
one  of  the  strips.  To  the  lower  end  of  the  cord  he  attached 
a  key  and  a  silk  ribbon.  By  means  of  the  ribbon  he  held 
the  cord  to  insulate  it  from  his  hand.  The  kite  soared  into 
the  clouds,  and  Franklin  and  his  son  stood  under  a  shed 
awaiting  the  coming  of  the  "electric  fire  "(Fig.  17).  Soon 

46 


FIG.     17 FRANKLIN  S    KITE    EXPERIMENT 

Taking  electricity  from  the  clouds. 


THE  STORY  OF  GREAT  INVENTIONS 


the  fibres  of  the  cord  began  to  bristle  up.  He  approached 
his  knuckles  to  the  key.  A  spark  passed.  He  brought  up 
a  Leyden  jar  and  charged  it  with  electricity  from  the 
cloud,  and  found  that  with  this  charge  he  could  do  every- 
thing that  could  be  done  with  electricity  from  his  machine. 
He  had  proved  the  identity  of  lightning  and  electricity. 

The  Lightning-Rod 

Some  time  before,  he  had  discovered  the  action  of  a 
point  in  discharging  electricity.  He  said:  "If  you  fix  a 
needle  to  the  end  of  a  gun-barrel  like  a  little  bayonet,  while  it 
remains  there  the  gun-barrel  cannot  be  electrified  so  as  to 
give  a  spark,  for  the  electric  fire  continually  runs  out  silently 
at  the  point."  In  the  dark  you  may  see  a  light  gather  upon 
the  point  like  that  of  a  firefly  or  glow-worm.  If  the  needle 
is  held  in  the  hand  and  brought  near  to  an  object  charged 
with  electricity,  the  object  is  quietly  discharged,  and  a 
light  may  be  seen  at  the  point  of  the  needle.  This  action 
of  points  explains  the  light  sometimes  seen  on  the  tops  of 
ships'  masts,  called  by  sailors  "Saint  Elmo's  fire,"  and 
perhaps,  also,  the  observation  of  Caesar  that,  in  a  certain 
African  war,  the  spears  of  the  Fifth  Roman  Legion  appeared 
tipped  with  fire. 

The  lightning-rod  was  the  outcome  of  Franklin's  observa- 
tions, and  this  was  the  first  practical  invention  relating  to 
electricity.  A  building  may  be  electrified  by  an  electrified 
cloud  passing  over  it.  If  the  building  is  protected  by 
pointed  rods,  the  electric  charge  will  quietly  escape  from 
the  points.  The  lower  ends  of  the  rods  must  be  in  the 

48 


THE    EIGHTEENTH   CENTURY 

moist  earth  below  the  surface.  The  lightning-rod  has  not 
proved  so  great  a  protection  as  Franklin  supposed  it  would. 
He  supposed  that  a  lightning- stroke  is  a  discharge  in  one 
direction  only ;  but  we  now  know  that  it  is  a  rapid  surging 
back  and  forth,  and  this  fact  accounts  for  the  failure  of  the 
lightning-rods  to  furnish  perfect  protection.  In  surging 
back  and  forth,  the  lightning  may  skip  from  the  lightning- 
rod  to  some  metal  object  within  the  building,  as  a  stove  or 
radiator.  The  lightning-rod  robbed  the  thunder-storm  of 
its  terrors  to  the  timid,  and  in  time  dispelled  the  supersti- 
tion of  people  who  believed  that  thunder  and  lightning  are 
evidence  of  the  wrath  of  the  Deity. 

Franklin  was  the  first  to  propose  an  answer  to  the  ques- 
tion: What  is  electricity?  He  believed  electricity  to  be  a 
subtle  fluid  existing  in  all  objects.  If  an  object  has  more 
than  a  certain  amount  of  this  fluid,  it  is  positively  elec- 
trified; if  less  than  this  amount,  it  is  negatively  electrified. 

The  "one-fluid"  theory  of  Franklin  was  soon  met  by  the 
"two-fluid"  theory  proposed  by  Robert  Symmer,  for 
Franklin's  theory  had  failed  to  explain  why  two  bodies 
negatively  electrified  should  repel  each  other.  According 
to  Symmer,  an  uncharged  body  contains  an  equal  quantity 
of  two  different  electrical  fluids.  An  excess  of  one  of  these 
produces  a  positive  charge,  an  excess  of  the  other  a  negative 
charge. 

Symmer 's  experiments  are  almost  ludicrous.  He  wore 
two  pairs  of  silk  stockings,  and  found  that  white  and  black 
silk  worn  together  became  strongly  electrified.  When  the 
two  stockings  worn  on  one  foot  were  pulled  off  together, 
and  then  separated,  they  were  found  to  be  electrified,  and 

49 


THE  STORY  OF  GREAT  INVENTIONS 

attracted  each  other  so  strongly  that  a  force  of  about  one 
pound  was  required  to  separate  them.  The  two  charges, 
negative  and  positive,  could,  however,  be  separated.  He 
thought,  therefore,  that  there  are  "two  electrical  powers," 
not  one,  as  Franklin  believed.  His  belief  was  strengthened 
by  examining  a  quire  of  paper  through  which  an  electric 
spark  had  passed,  and  finding  that  "the  edges  of  the  holes 
were  bent  two  different  ways,  as  if  the  hole  had  been  made 
in  the  quire  by  drawing  two  threads  in  contrary  directions 
through  it." 

There  was  a  long  controversy  regarding  the  two  theories, 
and  neither  quite  gained  possession  of  the  field.  Each  con- 
tained some  truth,  and  each  had  its  weak  points.  The 
two  had  more  in  common  than  men  at  that  time  thought. 

Galvani  and  the  Electric  Current 

Franklin  had  proven  that  there  is  electricity  in  the  atmos- 
phere, and  that  lightning  is  an  electric  discharge.  A  wide- 
spread interest  in  the  electricity  of  the  atmosphere  followed 
this  discovery.  Aloisio  Galvani,  a  physician  in  Bologna, 
Italy,  in  attempting  to  learn  the  effect  of  atmospheric  elec- 
tricity on  the  nerves  and  muscles  of  the  human  body,  made 
a  discovery  which  led  to  the  electric  battery  and  a  knowl- 
edge of  electric  currents. 

Having  dissected  a  frog,  he  laid  it  on  a  table  on  which 
stood  an  electrical  machine.  When  one  of  his  assistants 
touched  lightly  the  nerve  of  the  thigh  with  the  point  of  a 
knife  while  a  spark  was  drawn  from  the  electrical  machine, 
the  muscles  contracted  violently,  as  if  they  were  attacked 

50 


THE   EIGHTEENTH   CENTURY 

by  a  cramp.  When  he  held  the  knife  by  the  bone  handle, 
there  was  no  convulsion  as  there  was  when  he  held  it  by 
the  steel  blade. 

He  next  thought  it  important  to  find  out  if  lightning 
would  excite  contraction  of  the  muscles.  He  stretched  and 
insulated  a  long  iron  wire  in  the  open  air  on  the  housetop 
and,  as  a  storm  drew  near,  hung  on  it  a  dissected  frog.  To 
the  feet  he  fastened  another  long  iron  wire,  which  was  al- 
lowed to  dip  in  the  water  in  the  well.  "The  result,"  he  said, 
"came  about  as  we  wished.  As  often  as  the  lightning  broke 
forth,  the  muscles  were  thrown  into  repeated  violent  con- 
vulsions, so  that  always,  as  the  lightning  lightened  the  sky, 
the  muscle  contractions  and  movements  preceded  the 
thunder  and,  as  it  were,  announced  its  coming.  It  was 
best,  however,  when  the  lightning  was  strong,  or  the  clouds 
from  which  it  broke  forth  were  near  the  place  of  the  experi- 
ment." 

He  describes  his  greatest  experiment  as  follows:  "After 
we  had  investigated  the  power  of  atmospheric  electricity  in 
storms,  our  hearts  burned  with  the  desire  to  investigate 
the  daily  quiet  electricity  of  the  atmosphere.  Therefore,  as 
the  prepared  frogs,  hung  on  an  iron  railing  which  surrounded 
a  hanging  garden  on  our  house,  with  brass  hooks  inserted 
in  the  spinal  cord,  fell  into  convulsions  not  only  when  it 
lightened,  but  when  the  sky  was  calm  and  clear,  I  thought 
that  the  cause  of  these  contractions  was  the  changes  in  the 
electricity  of  the  atmosphere.  Then  for  hours,  yes,  even 
days,  I  observed  the  animals,  but  almost  never  a  movement 
of  the  muscles  could  be  seen.  At  last,  tired  with  such  fruit- 
less waiting,  I  began  to  press  the  brass  hooks,  which  were 

51 


THE   EIGHTEENTH   CENTURY 

fastened  in  the  spinal  cord,  against  the  iron  railing  to  see 
if  such  a  trick  would  cause  the  muscles  to  contract,  and  if 
instead  of  changes  in  the  atmospheric  electricity  any  other 
changes  would  have  any  influence.  I  observed,  indeed, 
vigorous  contractions,  but  none  which  could  be  caused  by 
the  condition  of  the  atmosphere." 

It  was  pressing  the  brass  hook  against  the  iron  railing, 
thus  forming  an  electric  battery,  that  caused  electricity  to 
pass  through  the  muscles  of  the  frog.  Galvani  did  not  know 
that  he  had  discovered  a  new  source  of  electricity.  He 
never  arrived  at  a  correct  explanation  of  his  results,  and 
never  knew  the  value  of  his  discovery. 

Volta  and  the  Electric  Battery 

It  was  left  for  Alexander  Volta  to  show  that,  in  Galvani' s 
experiment,  the  muscles  of  the  frog,  together  with  the  brass 
hook  and  the  iron  railing,  formed  an  electric  battery.  Volta 
showed  that  an  electric  charge  can  be  produced  merely  by 
bringing  two  different  metals  into  contact.  He  found  that, 
if  he  placed  copper  and  zinc  in  sulphuric  acid,  or  a  solution 
of  common  salt,  he  could  produce  a  continuous  flow  of 
electricity  (Fig.  18). 

In  the  beginning  of  the  year  1800  Volta  made  the  first 
electric  battery  (Fig.  19).  It  was  made  of  copper  and 
zinc  disks  placed  alternately,  with  a  piece  of  wet  cloth 
above  each  pair  of  disks.  With  his  column  of  disks  he 
could  obtain  a  strong  shock;  indeed,  many  shocks,  one 
after  the  other.  This  first  battery  of  Volta's  was  a  form 
of  "dry  battery."  Later  Volta  devised  his  "crown  of 

53 


THE  STORY  OF  GREAT  INVENTIONS 


FIG.     IQ THE    FIRST    ELECTRIC    BATTERY 

No.  i — A  battery  of  one  hundred  pairs  of  copper  and  zinc  disks. 
No.  2 — Two  such  batteries  connected. 

By  permission  of  the  Italian  Institute  of  Graphic  Arts,  Bergamo. 

cups,"  a  form  of  wet  battery  similar  to  some  batteries  in 
use  to-day.  Each  cup  contained  a  strip  of  copper  and  a 
strip  of  zinc  in  dilute  sulphuric  acid. 

Volta  did  not  know  the  real  use  of  the  liquid  in  his  bat- 
tery, nor  that  the  strength  of  the  current  depends  on  the 
rate  at  which  the  metal  is  dissolved  by  the  acid;  but  he 
had  discovered  the  electric  current,  and  with  this  discovery 
began  a  new  era  in  electrical  invention. 


Chapter   IV 

FARADAY   AND   THE   FIRST   DYNAMO 

MICHAEL  FARADAY,  a  London  newsboy,  the  son  of 
a  blacksmith,  became  the  inventor  of  the  dynamo,  and 
prepared  the  way  for  the  wonderful  electrical  inventions  of 
the  nineteenth  century.  He  began  his  career  as  a  book- 
binder's apprentice,  employing  his  spare  moments  in  read- 
ing the  books  he  was  binding.  One  of  these  books  led  him 
to  make  some  simple  experiments  in  chemistry.  He  also 
made  an  electrical  machine,  first  with  a  glass  bottle,  and 
afterward  with  a  glass  cylinder. 

While  an  apprentice  he  wrote  to  his  young  friend,  Ben- 
jamin Abbott:  "I  have  lately  made  a  few  simple  galvanic 
experiments,  merely  to  illustrate  to  myself  the  first  prin- 
ciples of  the  science.  I  was  going  to  Knight's  to  obtain 
some  nickel,  and  bethought  me  that  they  had  malleable 
zinc.  I  inquired,  and  bought  some — have  you  seen  any 
yet  ?  The  first  portion  I  obtained  was  in  the  thinnest  pieces 
possible.  It  was,  they  informed  me,  thin  enough  for  the 
electric  stick.  I  obtained  it  for  the  purpose  of  forming 
disks  with  which  and  copper  to  make  a  little  battery.  The 
first  I  completed  contained  the  immense  number  of  seven 
pairs  of  plates!!!  and  of  the  immense  size  of  halfpence 

55 


THE  STORY  OF  GREAT  INVENTIONS 

each!!!!!!  I,  sir,  I  my  own  self,  cut  out  seven  disks  of  the 
size  of  half  pennies  each!  I,  sir,  covered  them  with  seven 
halfpence,  and  I  interposed  between  them  seven,  or  rather 
six,  pieces  of  paper  soaked  in  a  solution  of  muriate  of  soda 
(common  salt).  But  laugh  no  longer,  dear  A.,  rather 
wonder  at  the  effects  this  trivial  power  produced." 

This  tiny  battery  made  of  half  pennies  with  zinc  disks 
and  salt  solution  would  decompose  a  certain  solution  which 
Faraday  tested.  A  larger  battery  made  of  copper  and  zinc 
disks  with  salt  solution  would  decompose  water  from  the 
cistern.  When  the  wires  from  the  larger  battery  were  put 
in  the  cistern-water  he  saw  a  dense  white  cloud  descending 
from  the  positive  wire,  and  bubbles  rising  from  the  negative 
wire.  This  action  continued  until  all  the  white  substance 
was  taken  out  of  the  water. 

Because  of  his  interest  in  science,  young  Faraday  attracted 
the  attention  of  a  Mr.  Dance,  a  member  of  the  Royal  In- 
stitution and  a  customer  of  his  master,  Mr.  Riebau.  Through 
the  kindness  of  Mr.  Dance  he  heard  four  lectures  by  Sir 
Humphry  Davy.  He  took  notes  on  the  lectures,  wrote 
them  out  carefully,  and  added  drawings  of  the  apparatus. 
These  notes  he  sent  to  Davy  with  a  letter  expressing 
the  wish  that  he  might  secure  employment  at  the  Royal 
Institution.  In  a  short  time,  after  a  warning  from  Sir 
Humphry  that  he  had  better  stick  to  his  business  of  book- 
binding, that  " Science  is  a  harsh  mistress,"  his  wish  was 
granted,  and  we  find  him  cleaning  and  caring  for  apparatus 
in  the  Royal  Institution  and  assisting  Davy  in  preparing 
for  his  lectures. 


FARADAY   AND    THE    FIRST    DYNAMO 


Count  Rumford 

Our  story  now  takes  us  back  to  the  time  of  the  American 
Revolution.  In  America,  we  find  a  young  man  of  nineteen, 
Benjamin  Thompson  by  name,  serving  as  major  in  the 
Second  Regiment  of  New  Hampshire.  The  appointment  of 
so  young  a  man  as  major,  and  his  evident  hold  on  the  gov- 
ernor's favor,  aroused  the  jealousy  of  the  older  officers. 
He  was  accused  of  being  unfriendly  to  the  cause  of  liberty. 
He  denied  the  charge,  and  was  acquitted  by  the  committee 
of  the  people  of  Concord.  A  mob  gathered  round  his  house, 
but  he  escaped.  Driven  from  his  refuge  in  his  mother's 
home,  he  fled  to  England,  leaving  his  wife  and  child.  Ap- 
pointed lieutenant-colonel  in  the  British  Army,  he  returned 
to  America  and  fought  against  his  former  friends. 

The  war  having  ended,  he  returned  to  England,  thence 
to  the  Continent,  intending  to  take  part  in  an  expected  war 
between  Austria  and  Turkey.  A  chance  meeting  with  a 
Bavarian  prince,  Maximilian,  changed  the  course  of  his  life. 
This  prince,  while  commanding  on  parade,  saw  Thompson 
among  the  spectators  mounted  on  a  fine  English  horse, 
and  addressed  him.  Thompson  informed  him  that  he  came 
from  serving  in  the  American  war.  The  prince,  pointing 
to  a  number  of  his  officers,  said:  " These  gentlemen  were  in 
the  same  war,  but  against  you.  They  belonged  to  the  Royal 
Regiment  of  Deux  Fonts,  that  acted  in  America  under  the 
orders  of  Count  Rochambeau."  Thompson  dined  with 
the  prince  and  French  officers.  They  conversed  of  war  and 
the  battles  in  which  they  met.  The  prince,  attracted  to  the 

57 


THE  STORY  OF  GREAT  INVENTIONS 

colonel,  induced  him  to  pass  through  Munich,  and  gave  him 
a  letter  to  his  uncle,  the  Elector  of  Bavaria. 

It  was  in  Bavaria,  the  country  to  which  such  unexpected 
turns  of  fortune  led  him,  that  his  greatest  work  was  done. 
He  entered  the  service  of  the  Duke  of  Bavaria  as  aide-de- 
camp. It  was  his  aim  while  in  the  service  of  the  Bavarian 
Government  to  better  the  condition  of  the  people.  He  in- 
troduced reforms  in  the  army,  used  the  soldiers  to  rid  the 
country  of  beggars  and  robbers,  and  took  steps  to  provide 
for  the  infirm  and  find  employment  for  the  strong,  his 
motto  being  that  people  can  best  be  made  virtuous  when 
first  made  happy. 

A  Military  Workhouse  was  opened  for  the  beggars,  and 
a  House  of  Industry  for  the  poor.  A  Military  Academy 
was  formed  with  a  view  to  the  free  education  of  young  peo- 
ple of  talent  for  the  public  service.  He  became  absorbed 
in  the  one  aim  of  helping  the  poor.  So  thorough  was  his 
devotion  to  the  people,  and  so  deeply  did  he  win  their 
affection,  that  when  he  was  dangerously  ill  a  multitude  of 
hundreds  went  in  procession  to  the  church  to  make  public 
prayers  for  his  recovery. 

He  saw  that  the  poor  may  be  helped  by  teaching  them 
to  save,  and  in  nothing  is  there  greater  need  of  saving  than 
in  fuel  and  heat.  In  the  kitchens  of  the  Military  Academy 
and  the  House  of  Industry  he  carried  out  a  series  of  experi- 
ments on  the  economy  of  fuel,  and  succeeded  in  greatly 
reducing  the  amount  of  fuel  needed  for  cooking  the  food. 
He  did  this  by  using  a  "closed  fireplace,"  the  forerunner 
of  the  stove.  The  closed  fireplace  was  in  reality  a  brick 
stove,  and  was  a  great  improvement  over  the  open  chimney 

58 


FARADAY    AND    THE    FIRST    DYNAMO 

fireplaces  then  in  common  use.  He  made  the  covers  of 
the  cooking  utensils  double,  to  save  the  heat,  for  he  had 
found  that  heat  cannot  escape  through  confined  air. 

Benjamin  Thompson  was  knighted  by  George  III.,  and 
in  1791  he  was  made  a  Count  of  the  Holy  Roman  Empire, 
and  is  known  to  the  world  of  science  as  Count  Rumford. 


Count  RumforcTs  Experiment  with  the  Cannon 

While  in  the  service  of  the  Duke  of  Bavaria,  it  became 
his  duty  to  organize  the  field  artillery.  To  provide  cannon 
for  this  purpose,  he  erected  a  foundry  and  machine-shops. 
Being  alert  for  any  unusual  fact  relating  to  heat,  he  observed 
the  very  high  temperature  produced  by  the  boring  of  the 
cannon.  He  was  eager  to  learn  how  so  much  heat  could 
be  produced.  For  this  purpose  he  took  a  cannon  in  the 
rough,  as  it  came  from  the  foundry,  fixed  it  in  the  machine 
used  for  boring,  and  caused  the  cannon  to  be  turned  by 
horses  while  a  blunt  borer  was  forced  against  the  end  of  the 
cannon.  He  first  tested  the  temperature  of  the  metal  itself 
as  it  turned.  Then  he  surrounded  the  end  of  the  cannon 
with  water  in  an  oblong  box  fitted  water-tight  (Fig.  20). 

The  cannon  had  been  turning  but  a  short  time  when  he 
found  by  putting  his  hand  in  the  water  that  heat  had  been 
produced.  In  two  hours  and  thirty  minutes  the  water 
actually  boiled.  Astonishment  was  expressed  in  the  faces 
of  the  bystanders  on  seeing  so  large  a  quantity  of  water 
heated  and  actually  made  to  boil  without  any  fire. 

4 'Heat,"  Count  Rumford  said,  "may  thus  be  produced 
merely  by  the  strength  of  a  horse,  and,  in  case  of  necessity, 

59 


FARADAY   AND    THE    FIRST    DYNAMO 


this  heat  might  be  used  in  cooking  victuals.  But  no  cir- 
cumstance can  be  imagined  in  which  there  is  any  advan- 
tage in  this  method  of  procuring  heat,  for  more  heat  might 
be  obtained  by  burning  the  fodder  which  the  horse  would 
eat."  The  meaning  ot  this  last  remark  was  not  understood 
until  the  time  of  Robert  Mayer,  about  fifty  years  later. 
Rumford  had  found  that  the  work  of  a  horse  can  produce 
heat,  and  heat,  in  a  steam-engine,  can  do  the  work  of  a 
horse.  Thus  surely,  though  slowly,  men  were  learning  of 
the  forces  that  move  the  world  and  do  man's  bidding. 

Count  Rumford,  true  to  his  adopted  land,  returned  to 
London  and  became  the  founder  of  the  Royal  Institution 
in  which  Faraday  and  his  successors  have  achieved  such 
marvellous  results.  He  believed  that  the  poor  can  be  helped 
in  no  better  way  than  by  giving  them  knowledge,  so  that 
they  can  better  their  own  condition.  For  this  purpose 
he  founded  the  Royal  Institution.  Here  he  intended  that 
men  skilled  in  discovery  should  gain  new  knowledge  that 
would  add  to  the  comfort  and  happiness  of  the  people. 

Davy 

In  the  English  coal-fields  many  accidents  due  to  the 
burning  of  fire-damp  had  occurred.  Fire-damp  is  caused 
by  gas  issuing  from  the  coal.  On  the  approach  of  a  flame 
this  gas  catches  fire,  and  as  it  burns  it  produces  a  violent 
wind,  driving  the  flame  before  it  through  the  mine.  Miners 
were  scorched  to  death,  suffocated,  or  buried  under  ruins 
from  the  roof.  Hundreds  of  miners  had  been  killed.  No 
means  of  lighting  the  mines  in  safety  had  been  devised. 

61 


THE  STORY  OF  GREAT  INVENTIONS 

Sir  Humphry  Davy,  Professor  of  Chemistry  in  the  Royal 
Institution,  was  appealed  to.  After  many  experiments  he 
devised  a  "safe  lamp,"  which  was  a  common  miner's  lamp 
enclosed  in  a  wire  gauze.  This  proved  a  perfect  protection 
from  fire-damp,  and  the  Davy  safety  lamp  has  been  used 
by  miners  the  world  over  for  more  than  a  century. 

But  Davy's  best  work  was  with  the  electric  battery. 
Some  of  the  facts  most  familiar  to  us  were  discovered  by 
him.  Volta  had  contended  that  the  contact  of  the  metals 
in  a  battery  produces  a  current,  that  the  liquid  merely 
carries  the  electricity  from  one  metal  plate  to  the  other. 
But  Davy  proved  that  there  can  be  no  current  without 
chemical  action.  Whenever  we  put  two  metals  in  an  acid 
or  other  solution  that  will  dissolve  one  metal  faster  than 
the  other,  and  connect  the  metals  with  a  wire,  an  electric 
current  is  produced.  If  we  use  water  with  silver  and  gold, 
there  is  no  current,  because  water  will  not  dissolve  either 
the  silver  or  the  gold. 

Davy  discovered  the  metal,  potassium,  by  means  of  his 
electric  battery.  Potassium  is  found  in  common  potash 
and  saltpetre,  and,  when  separated,  is  a  very  soft  metal. 
The  newly  discovered  metal  aroused  great  interest  in  other 
countries.  When  Napoleon  heard  of  it,  he  inquired  im- 
petuously how  it  happened  the  discovery  had  not  been 
made  in  France.  On  being  told  that  in  France  there  had 
not  been  made  an  electric  battery  of  sufficient  power,  he 
exclaimed:  "Then  let  one  be  instantly  made  without  re- 
gard to  cost  or  labor."  His  command  was  obeyed,  and  he 
was  called  to  witness  the  action  of  the  new  battery.  Before 
any  one  could  interfere  he  placed  the  ends  of  the  wires 

62 


FARADAY    AND    THE    FIRST    DYNAMO 


under  his  tongue  and  received  a  shock  that  nearly  deprived 
him  of  sensation.  On  recovering  he  left  the  laboratory 
without  a  word,  and  was  never  afterward  heard  to  refer  to 
the  subject. 

Davy  made  many  great  discoveries,  but  the  greatest  was 
his  discovery  of  Faraday. 

A  journey  on  the  Continent  with  Davy  was  an  event  in 
the  life  of  Faraday,  who  up  to  that  time  had  never  to  his 
own  recollection  travelled  twelve  miles  from  London.  On 
this  journey  he  met  Volta,  whom  he  describes  as  "an  hale 
elderly  man,  very  free  in  conversation."  He  visited  the 
Academy  del  Cimento,  in  Florence,  and  wrote:  "Here  was 
much  to  excite  interest;  in  one  place  was  Galileo's  first 
telescope,  that  with  which  he  discovered  Jupiter's  satellites. 
It  was  a  simple  tube  of  wood  and  paper,  about  three  and  a 
half  feet  long,  with  a  lens  at  each  end.  There  was  also 
the  first  lens  which  Galileo  made.  It  was  set  in  a  very 
pretty  frame  of  brass,  with  an  inscription  in  Latin 
on  it." 

Faraday  crossed  the  Alps  and  the  Apennines,  climbed 
Vesuvius,  visited  Rome,  and  saw  a  glow-worm.  The  last  he 
thought  as  wonderful  as  the  first. 

Shortly  after  his  return  to  London  he  fell  in  love.  Now, 
Faraday  had  determined  that  he  would  not  be  conquered 
by  the  master  passion.  In  fact,  he  had  written  various 
aspersions  on  love,  of  which  the  following  is  a  sample: 

"What  is  the  pest  and  plague  of  human  life? 
And  what  the  curse  that  often  brings  a  wife? 

Tis  Love. 
5  63 


THE  STORY  OF  GREAT  INVENTIONS 

What  is't  directs  the  madman's  hot  intent, 
For  which  a  dunce  is  fully  competent? 
What's  that  the  wise  man  always  strives  to  shun, 
Though  still  it  ever  o'er  the  world  has  run? 
Tis  Love." 

But  he  reckoned  not  with  his  own  heart.  It  is  not  long 
until  we  find  him  writing  to  Miss  Sarah  Barnard,  a  bright 
girl  of  twenty-one:  ''You  have  converted  me  from  one 
erroneous  way,  let  me  hope  you  will  attempt  to  correct 
what  others  are  wrong.  .  .  .  Again  and  again  I  attempt  to 
say  what  I  feel,  but  I  cannot.  Let  me,  however,  claim  not 
to  be  the  selfish  being  that  wishes  to  bend  your  affections 
for  his  own  sake  only.  In  whatever  way  I  can  minister  to 
your  happiness,  either  by  close  attention  or  by  absence,  it 
shall  be  done.  Do  not  injure  me  by  withdrawing  your 
friendship  or  punish  me  for  aiming  to  be  more  than  a  friend 
by  making  me  less." 

They  were  married  and  lived  in  rooms  at  the  Royal 
Institution.  No  poet  ever  loved  more  tenderly  than  Fara- 
day. Truly,  science  does  not  dry  up  the  heart's  blood. 
At  the  age  of  seventy-one  he  wrote  to  his  wife  while  absent 
from  home  for  a  few  days:  " Remember  me;  I  think  as 
much  of  you  as  is  good  for  either  you  or  me.  We  cannot 
well  do  without  each  other.  But  we  love  with  a  strong 
hope  of  love  continuing  ever." 

Faraday's  Electrical  Discoveries 

Now  we  shall  turn  to  Faraday's  electrical  discoveries 
and  inventions.  Men  had  long  known  that,  in  houses  that 

64 


FARADAY   AND   THE   FIRST   DYNAMO 

have  been  struck  by  lightning,  steel  objects  such  as  knives 
and  needles  are  sometimes  found  to  be  magnetized.  Ships 
struck  by  lightning  had  found  their  compass-needles  point- 
ing south  instead  of  north,  or  wandering  in  direction  and 
worthless.  Men  had  wondered  how  an  electrical  discharge 
could  magnetize  steel.  They  had  tried  the  spark  of  the 
electrical  machine  with  no  definite  result.  Franklin,  in  his 
experiment  of  magnetizing  a  steel  needle  by  passing  an 
electric  spark  through  it,  could  not  tell  before  the  spark  was 
passed  through  the  needle  which  end  would  be  the  north 
pole.  There  was  no  seeming  connection  between  the  di- 
rection of  the  electric  discharge  and  the  polarity  of  the 
needle.  After  the  discovery  of  the  electric  battery,  men 
tried  to  discover  a  relation  between  the  electric  current  and 
magnetism. 

Oersted  and  Electromagnetism 

The  first  success  in  this  direction  was  achieved  by  Hans 
Christian  Oersted,  a  native  of  Denmark.  Poverty  impelled 
his  father  to  take  him  from  school  at  the  age  of  twelve  and 
place  him  in  an  apothecary's  shop.  The  boy,  Hans,  found 
delight  in  the  chemical  work  of  the  apothecary.  His  eager- 
ness to  learn  and  the  pressure  of  poverty  led  him  to  neglect 
the  usual  sports  of  boyhood  and  devote  his  leisure  time  to 
reading  and  study.  Again  he  entered  school,  and,  though 
paying  his  way  by  his  own  work,  he  graduated  with  honor 
from  the  University  of  Copenhagen.  He  was  appointed 
Professor  of  Physics  in  this  university,  and  here  he  made 
his  first  great  discovery  in  electromagnetism. 

After  working  for  seven  years  to  discover  a  relation  be- 
5  65 


THE  STORY  OF  GREAT  INVENTIONS 

tween  current  electricity  and  magnetism,  he  made  a  dis- 
covery which  proved  to  be  the  first  step  in  the  invention  of 
the  dynamo.  He  was  using  a  magnetic  compass,  which  is 
a  small  magnetic  needle  balanced  on  a  steel  point.  The 
needle  points  nearly  north  and  south  unless  disturbed  by 
a  magnet  brought  near  it.  He  had  tried  to  find  if  a  wire 
through  which  a  current  is  flowing  would  disturb  the  com- 
pass as  a  magnet  does.  He  had  tried  placing  the  wire  east 
and  west,  thinking  the  compass-needle  would  follow  the 


FIG.    21 OERSTED  S    EXPERIMENT 

An  electric  current  flowing  over  the  compass-needle  toward  the  north 
causes  the  needle  to  turn  until  it  points  nearly  west. 

By  permission  of  Joseph  G.  Branch. 

wire  as  it  does  a  magnet.  One  day,  while  lecturing  to  his 
students,  it  occurred  to  him  for  the  first  time  to  place  the 
wire  north  and  south  over  the  compass-needle.  He  was 
surprised  and  perplexed  as  he  did  so  to  see  the  needle 
swing  round  and  point  nearly  east  and  west  (Fig.  21).  On 
reversing  the  current  the  needle  swung  in  the  opposite 
direction.  He  had  discovered  the  magnetic  action  of  an 
electric  current.  It  was  learned  soon  afterward  that  a  coil 
of  wire  with  an  electric  current  flowing  through  it  acts  like 

66 


FARADAY   AND   THE   FIRST   DYNAMO 


a  magnet,  and  that  a  current  flowing  around  a  bar  of  soft 
iron  makes  the  iron  a  magnet  (Figs.  22  and  23). 


FIG  22. A  COIL  WITH    A   CURRENT 

FLOWING    THROUGH    IT    ACTS 
LIKE    A    MAGNET 

The  coil  is  picking  up  iron  filings. 


FIG.  23 A  BAR  OF  SOFT  IRON  WITH 

A   CURRENT    FLOWING    AROUND 
IT    BECOMES  A  MAGNET 


Ampere 

The  news  of  Oersted's  discovery  aroused  great  interest 
throughout  Europe.  Soon  aftei  its  announcement  in  France, 
Andre  Marie  Ampere  made  a  discovery  of  equal  importance. 
Oersted  had  discovered  electromagnet  ism.  Ampere  discov- 
ered electrical  power  or  motion  produced  by  an  electrical 
current. 

The  youth  of  Ampere  was  passed  amid  the  stormy  scenes 
of  the  French  Revolution.  His  father  had  moved  from  his 

67 


THE  STORY  OF  GREAT  INVENTIONS 


country  home  to  Lyons  and  become  a  justice  of  the  peace. 
In  the  destruction  of  the  city  of  Lyons  during  the  Reign  of 
Terror  he  lost  his  head  under  the  guillotine. 

The  blow  was  too  great  for  Ampere,  then  a  youth  ot 
eighteen.  He  had  been  a  precocious  child,  advanced  be- 
yond his  years  in  all  the  studies  of  the  schools.  But  now 
his  strong  mind  failed.  For  a  year  he  wandered  about  me- 
chanically piling  up  heaps  of  sand  or  gazing  upon  the  sky. 
Then  his  mental  power  returned,  and  he  took  up  with  eager- 
ness the  study  of  botany  and  poetry. 

He  became  a  professor  in  the  Polytechnic  School  in  Paris, 
and  it  was  while  teaching  in  this  school  that  he  made  his 
great  discoveries.  He  found  that  two  coils  of  wire  can  be 
made  to  attract  or  repel  each  other  by  an  electric  current. 
If  the  current  flows  through  the  two  coils  in  the  same  direc- 
tion, they  attract  each  other  (Fig.  24).  If  the  current  flows 


FIG.    24 TWO     COILS     WITH     CUR- 
RENTS FLOWING  IN  SAME  DIREC- 
TION   ATTRACT    EACH    OTHER 


FIG.    25 TWO     COILS     WITH     CUR- 
RENTS FLOWING  IN  OPPOSITE    DI- 
RECTIONS  REPEL  EACH  OTHER 


68 


FARADAY  AND  THE  FIRST  DYNAMO 

in  opposite  directions  through  the  coils,  they  repel  each 
other  (Fig.  25).  This  is  not  very  strange  to  us,  for  we 
know  that  a  coil  with  a  current  flowing  through  it  acts  just 
like  a  magnet.  Each  coil  then  has  a  north  pole  and  a  south 
pole.  If  the  coils  are  placed  so  that  the  two  north  poles  or 
the  two  south  poles  are  together,  they  will  repel  each  other. 
If  the  north  pole  of  one  coil  is  near  the  south  pole  of  the 
other,  they  will  attract  each  other. 

Ampere  believed  that  electric  currents  are  flowing  around 
within  the  earth,  and  that  the  earth  has  a  north  and  a  south 
magnetic  pole  for  the  same  reason  that  a  coil  of  wire  has 
magnetic  poles;  that  these  poles  are  caused  by  the  currents 
flowing  around  in  the  earth  just  as  the  poles  of  the  coil  are 
caused  by  the  current  flowing  around  in  the  coil. 

We  do  honor  to  the  name  of  Ampere  whenever  we  measure 
an  electric  current,  for  electric  currents  are  measured  in 
"amperes." 

Arago 

Another  important  discovery  was  made  by  a  young 
Frenchman,  Francois  Arago,  within  a  year  of  the  time  when 
Oersted  and  Ampere  made  their  discoveries.  The  three 
great  discoveries  of  these  men  were  made  in  the  years  1819 
and  1820.  The  youth  of  Arago  was  full  of  adventure.  He 
had  assisted  in  making  a  survey  in  the  Pyrenees,  the  haunt 
of  daring  robber-bands.  Twice  in  his  cabin  he  was  visited 
by  a  chief  of  a  robber-band  who  claimed  to  be  a  custom- 
house guard.  On  the  second  visit  he  said  to  the  robber: 
"Your  position  is  perfectly  known  to  me.  I  know  that  you 
are  not  a  custom-house  guard.  I  have  learned  that  you 

69 


THE  STORY  OF  GREAT  INVENTIONS 


are  the  chief  of  the  robbers  of  the  country.  Tell  me  whether 
I  have  anything  to  fear  from  your  confederates."  The 
robber  replied:  "The  idea  of  robbing  you  did  occur  to  us; 
but,  on  the  day  that  we  molested  an  envoy  from  the  French, 
they  would  direct  against  us  several  regiments  of  soldiers, 
and  we  are  not  so  strong  as  they.  Allow  me  to  add  that  the 
gratitude  which  I  owe  you  for  the  night's  shelter  is  your 
surest  guarantee." 

At  a  later  time,  when  war  between  Spain  and  France  was 
threatened,  he  was  accused  of  being  a  spy,  and  a  mob  was 

formed  to  put  him  out 
of  the  way.  He  escaped 
in  disguise  through  the 
midst  of  the  mob  and 
boarded  a  Spanish  ship. 
He  was  carried  to  Moroc- 
co, ran  the  gantlet  of 
bloodthirsty  Mussulmans 
in  Algiers,  escaped  death 
by  a  hair's-breadth,  and 
through  it  all  clung  to 
the  papers  which  record- 
ed the  results  of  the  sur- 
vey in  the  mountains, 
FIG.  26— ARAGO'S  EXPERIMENT  an(j  delivered  them  in 

When  the  copper  plate  whirls  the  mag-     safety    to    the     office    -of 
net  whirls  also,  though  it  does  not  touch  . 

the  copper  plate.  the  Bureau  of  Longitude 

in  Paris. 

Arago  made  a  discovery  which,  with  those  of  Oersted  and 
Ampere,  prepared  the  way  for  Faraday's   great  electrical 

70 


FARADAY   AND   THE   FIRST    DYNAMO 


discoveries  and  the  invention  of  the  dynamo.  He  found  that  a 
plate  of  copper  whirling  above  or  below  a  magnetic  needle  will 
draw  the  needle  after  it  (Fig.  26) .  He  could  make  the  speed  of 
the  whirling  copper  plate  so  great  that  the  needle  would  whirl 
rapidly,  following  the 
copper  plate.  Faraday 
was  the  first  to  explain 
Arago's  experiment. 

Faraday's  First  Electric 
Motor 

Faraday's  first  electri- 
cal discovery  was  made 
soon  after  that  of  Ara- 
go.  Oersted  had  proven 
that  an  electric  current 
acts  on  a  magnet.  The 
magnet  turns  at  right 
angles  to  the  wire.  Far- 
aday saw  that  this  is  be- 
cause the  north  pole  of 
the  magnet  tries  to  go 
round  the  wire  in  one 
direction,  and  the  south 
pole  tries  to  go  round 
in  the  opposite  direc- 
tion. He  placed  a  magnet  on  end  in  a  dish  of  mercury, 
with  one  pole  of  the  magnet  above  the  mercury,  and  found 
that  the  magnet  would  spin  round  a  wire  carrying  a  cur- 
rent. When  the  current  acts  on  one  pole  of  the  magnet 

71 


FIG.    27 ONE     POLE     OF    A     MAGNET     SPINS 

ROUND    A    WIRE    THROUGH    WHICH    AN 
ELECTRIC    CURRENT     FLOWS 


THE  STORY  OF  GREAT  INVENTIONS 

only,  the  magnet  spins  round  the  wire  (Fig.  27).  So  Fara- 
day's first  electrical  discovery  prepared  the  way  for  the 
electric  motor. 

An  Electric  Current  Produced  by  a  Magnet 

He  had  written  in  his  note-book:  "Convert  magnetism 
into  electricity."  An  electric  current  would  magnetize  iron. 
Would  not  a  magnet  produce  an  electric  current  ?  This 
was  his  problem. 

He  connected  a  coil  of  wire  to  an  instrument  that  would 
tell  when  a  current  was  flowing,  and  placed  a  magnet  in  the 
coil.  Others  had  claimed,  and  Faraday  at  first  believed,  that 
a  current  would  flow  while  the  magnet  lay  quiet  within  the 
coil.  But  Faraday  was  alert  for  the  unexpected,  and  the 
unexpected  happened.  For  an  instant,  as  he  thrust  the 
magnet  into  the  coil,  his  instrument  showed  that  a  current 
was  flowing.  Again,  as  he  drew  the  magnet  quickly  from 
the  coil,  a  current  flowed,  but  in  the  opposite  direction 
(Fig.  28).  From  this  simple  experiment  has  grown  the 
alternating-current  machinery  by  which  the  power  of 
Niagara  is  made  to  light  cities  and  drive  electric  cars  at  a 
distance  of  many  miles. 

A  friend  of  Faraday,  on  learning  of  this  discovery,  wrote 
the  following  impromptu  lines: 

"Around  the  magnet  Faraday 
Was  sure  that  Volta's  lightnings  play. 

But  how  to  draw  them  from  the  wire? 
He  took  a  lesson  from  the  heart:  t* 

'Tis  when  we  meet,  'tis  when  we  part, 
Breaks  forth  the  electric  fire." 
72 


FARADAY   AND   THE   FIRST   DYNAMO 


FIG.  38 WHEN    A  MAGNET    IS    THRUST    INTO   A  COIL  OF    WIRE    IT   CAUSES   A 

CURRENT    TO    FLOW   IN    THE    COIL,     BUT    THE    CURRENT    FLOWS 

ONLY   WHILE    THE    MAGNET    IS    MOVING 
Drawing  reproduced  by  permission  of  Joseph  G.  Branch. 

A  magnet  will  produce  an  electric  current  in  a  wire,  but 
only  when  the  magnet  or  the  wire  is  in  motion. 

Detecting  and  Measuring  an  Electric  Current 

The  instrument  which  Faraday  used  to  detect  a  current 
was  derived  from  Oersted's  experiment.  When  a  current 
flows  in  a  north-and- south  direction  over  a  compass-needle, 
the  needle  swings  round.  When  the  current  stops  flowing 

73 


THE  STORY  OF  GREAT  INVENTIONS 

the  needle  swings  back  to  the  north-and- south  position. 
The  effect  on  the  needle  is  stronger  if  the  current  flows 
through  a  coil  of  wire  and  the  coil  is  placed  in  a  north-and- 
south  position  around  the  needle  (Fig.  29).  The  stronger 
the  current  flowing  through  the  coil  the  farther  the  needle 
will  turn  from  the  north-and- south  position. 


FIG.    29 A    COIL    OF    WIRE    AROUND    A    COMPASS-NEEDLE 

The  needle  tells  when  a  current  is  flowing,  and  how  strong  the  current  is. 

The  coil  and  the  needle  together  are  called  a  galvanom- 
eter, and  may  be  used  to  tell  when  a  current  is  flowing, 
and  also  to  indicate  the  strength  of  the  current. 

An  Electric  Current  Produced  by  the  Magnetic  Field  of  Another 

Current 

Faraday  had  found  that  a  current  flowing  around  a  piece 
of  iron  will  make  the  iron  a  magnet,  and  that  a  magnet  in 
motion  will  cause  a  current  to  flow  in  a  wire.  It  seemed 

74 


FARADAY   AND   THE   FIRST   DYNAMO 

to  him  that  a  second  wire  placed  near  the  first  should  have 
a  current  produced  in  it  without  the  presence  of  iron.  He 
wound  two  coils  of  copper  wire  upon  the  same  wooden  spool. 
The  wire  of  the  two  coils  he  separated  with  twine  and  calico. 
One  coil  was  connected  with  a  galvanometer,  the  other  with 
a  battery  of  ten  cells,  yet  not  the  slightest  turning  of  the 
needle  could  be  observed.  But  he  was  not  deterred  by  one 
failure.  He  raised  his  battery  from  ten  cells  to  one  hundred 
cells,  but  without  avail.  The  current  flowed  calmly  through 
the  battery  wire  without  producing,  during  its  flow,  any 
effect  upon  the  galvanometer.  During  its  flow  was  the 
time  when  an  effect  was  expected. 

Again  the  unexpected  happened.  At  the  instant  of  mak- 
ing contact  with  the  battery  there  was  a  slight  movement 
of  the  needle.  When  the  contact  was  broken,  another  slight 
movement,  but  in  the  opposite  direction  to  the  first  (Fig. 
30).  The  current  in  one  wire  caused  a  current  to  flow 
in  the  other,  but  the  current  in  the  second  wire  con- 
tinued for  an  instant  only  at  the  making  and  breaking 
of  the  contact  with  the  battery.  This  was  the  begin- 
ning of  the  induction-coil  used  to-day  in  wireless  teleg- 
raphy. 

What  was  the  secret  of  it  ?  Simply  this :  that  a  current 
in  one  wire  will  cause  a  current  to  flow  in  another  wire  near 
it,  but  only  while  the  current  in  the  first  wire  is  changing. 
That  is,  at  the  instant  when  the  first  wire  is  connected  to 
the  battery,  or  its  connection  broken,  a  current  is  induced 
in  the  second  wire.  There  is  no  battery  or  other  source  of 
current  connected  to  the  second  wire;  but  a  current  flows 
in  this  wire  because  it  is  near  a  wire  in  which  a  current  is 

75 


THE  STORY  OF  GREAT  INVENTIONS 

rapidly  starting  and  stopping.  When  these  two  wires  are 
wound  in  coils,  together  they  form  an  induction-coil.  The 
wire  which  we  have  called  the  first  wire  forms  the  ' '  primary  " 


FIG.  30 — FARADAY'S  INDUCTION-COIL 

Starting  and  stopping  the  battery  current  in  the  primary  coil  causes 
a  changing  magnetic  field,  and  this  causes  a  current  to  flow  in  the 
secondary  coil. 

Drawing  reproduced  by  permission  of  Joseph  G.  Branch. 

coil,  and  the  one  we  have  called  the  second  wire  forms  the 
"secondary"  coil.  By  repeatedly  making  and  breaking  the 
circuit  in  the  primary  coil  we  get  an  alternating  current  in 

76 


FARADAY   AND   THE   FIRST   DYNAMO 

the  secondary  coil.     Fig.  31  is  from  a  photograph  of  some 
of  the  coils  actually  used  by  Faraday. 


Faraday's  Dynamo 

To  invent  a  new  electrical  machine  was  Faraday's  next 
aim.  Arago's  disk  of  copper  whirling  near  a  magnet  had 
a  current  induced  in  it,  so  Faraday  thought.  It  was  the 


FIG.  31 HISTORICAL  APPARATUS  OF  FARADAY  IN    THE    ROYAL    INSTITUTION 

Some  of  Faraday's  transformer  coils  are  shown  here.     The  instrument 
on  the  left  in  a  glass  case  is  his  galvanometer. 

action  of  this  induced  current  which  caused  the  magnet  to 
follow  the  whirling  disk.  Could  the  current  in  Arago's  disk 
be  collected  and  caused  to  flow  through  a  wire  ?  He  placed 
a  copper  disk  between  the  poles  of  a  magnet.  One  galva- 

77 


THE  STORY  OF  GREAT  INVENTIONS 

nometer  wire  passed  around  the  axis  of  the  disk,  the  other  he 
held  in  contact  with  the  edge.  He  whirled  the  disk.  The 
galvanometer  needle  moved.  A  current  was  flowing  in  the 
disk  as  it  whirled.  The  current  from  the  whirling  disk 
flowed  through  the  galvanometer.  Faraday  had  discovered 
the  dynamo  (Fig.  32). 


FIG.   32 — FARADAY'S  FIRST  DYNAMO 

A  current  flows  in  the  copper  disk  as  it  whirls  between  the  poles 
of  the  magnet. 

By  permission  of  Joseph  G.  Branch. 
78 


FARADAY   AND   THE   FIRST   DYNAMO 

All  this  work  occupied  but  ten  days  in  the  autumn  of 
1831,  though  years  of  preparation  had  gone  before.  In 
these  ten  days  the  foundation  was  laid  for  the  induct  ion- 


FIG.  33 FARADAY  S    LABORATORY,  WHERE    THE    FIRST    DYNAMO    WAS    MADE 

From  the  water-color  drawing  by  Miss  Harriet  Moore. 

coil,  modern  dynamo  -  electric  machinery,  and  electric 
lighting.  Fig.  33  shows  the  laboratory  in  which  Faraday 
did  this  work. 

Faraday  continued  to  explore  the   field  opened  up  be- 
fore him.     In  one  experiment  two  small  pencils  of  charcoal 
lightly  touching  were  connected  to  the  ends  of  a  secondary 
G  79 


THE  STORY  OF  GREAT  INVENTIONS 


coil.  A  spark  passed  between  the  charcoal  points  when 
the  primary  circuit  was  closed.  This  was  the  first  trans- 
former producing  a  tiny  electric  light  (Fig.  34). 

Faraday  discovered  the  induction-coil,  the  dynamo,  and 
the  transformer,  and  he  showed  that,  in  each  of  these,  it  is 
magnetism  which  produces  the  electric  current.  He  had 


SECONDARY/ 

COIL 


FIG.    34 THE    FIRST    TRANSFORMER 

discovered  the  secret  when  he  obtained  a  current  by  thrust- 
ing a  magnet  into  a  coil  of  wire.  The  space  about  a  magnet 
in  which  the  magnet  will  attract  iron  he  called  the  ' '  magnetic 
field"  (Figs.  35  and  36).  In  every  case  of  magnetism  caus- 
ing an  electric  current  to  flow  in  a  coil  of  wire,  the  coil  is 
in  a  magnetic  field,  and  the  magnetic  field  is  changing — that 

80 


FARADAY   AND   THE   FIRST   DYNAMO 


FIG.  35 — THE  "MAGNETIC   FIELD"  is  THE   SPACE  AROUND  A  MAGNET  IN 

WHICH    IT    WILL   ATTRACT   IRON 

The  iron  filings  over  the  magnet  arrange  themselves  along  the  "lines 
of  force." 

is,  the  magnetic  field  is  made  alternately  stronger  and  weak- 
er, or  the  coil  moves  across  the  magnetic  field.  The  point  is 
that  magnetism  at  rest  will  not  produce  an  electric  current. 
There  must  be  a  changing  magnetic  field  or  motion.  In 
Faraday's  dynamo  a  copper  disk  whirled  between  the  poles 


FIG.    36 MAGNETIC    FIELD    OF    A    HORSESHOE    MAGNET 

81 


THE  STORY  OF  GREAT  INVENTIONS 


of  a  magnet  and  the  whirling  of  the  disk  in  the  magnetic 
field  caused  an  electric  current.  In  the  modern  dynamo  it 
is  the  whirling  of  a  coil  of  wire  in  a  magnetic  field  that 
causes  a  current  to  flow.  In  the  induction-coil  it  is  the 
change  in  the  magnetic  field  that  causes  a  current  to  flow 
in  the  secondary  coil.  A  coil  of  wire  with  an  electric 
current  flowing  through  it  will  attract  iron  like  a  magnet. 
The  primary  coil  with  a  current  from  a  battery  flowing 
through  it  acts  in  all  respects  like  a  magnet;  but  as  soon 
as  the  current  ceases  to  flow  the  magnetic  field  disappears — 
the  coil  is  no  longer  a  magnet.  When  we  make  and  break 
the  connection  between  the  primary  coil  and  the  battery, 
then,  we  repeatedly  make  and  destroy  the  magnetic  field, 
and  this  changing  magnetic  field  causes  a  current  to  flow 
in  the  secondary  coil.  The  induction-coil  is  one  form  of 
transformer.  We  shall  see  later  how  the  dynamo  and  the 
transformer  developed  in  the  nineteenth  century. 

When  a  boy,  Faraday  had  passed  the  current  from  his 
little  battery  through  a  jar  of  cistern-water,  and  saw  in  the 
water  a  " dense  white  cloud"  descending  from  the  positive 
wire,  and  bubbles  arising  from  the  negative  wire.  Some- 
thing was  being  taken  out  of  the  water  by  the  electric  cur- 
rent. When  he  tried  the  experiment  later  in  his  laboratory, 
he  found  that,  whenever  an  electric  current  is  passed  through 
water,  bubbles  of  two  gases,  oxygen  and  hydrogen,  rise 
through  the  water.  He  found  that  if  the  current  is  made 
stronger  the  bubbles  are  formed  faster.  The  water  in  time 
disappears,  for  it  has  been  changed  or  "decomposed"  into 
the  two  gases. 

It  was  the  current  from  a  battery  that  would  decompose 

82 


FARADAY   AND   THE   FIRST   DYNAMO 

water.  The  electricity  from  the  electrical  machine  would 
do  other  things  that  he  had  never  seen  a  battery  current 
do.  "Do  the  battery  and  the  electrical  machine  produce 
different  kinds  of  electricity,  or  is  electricity  one  and  the 
same  in  whatever  way  it  is  produced  ?"  This  was  the  query 
that  troubled  him.  The  answer  to  this  question  had  been 
so  uncertain  that  the  effect  of  the  voltaic  battery  had  been 
termed  "galvanism,"  while  that  of  the  friction  machine 
retained  the  name  "electricity." 

Faraday  tried  many  experiments  in  searching  for  an 
answer  to  this  question.  He  found  that  the  electricity  of 
the  machine  will  produce  the  same  effect  as  that  of  a  bat- 
tery if  the  machine  is  compelled  to  discharge  slowly.  An 
electrical  machine  or  a  battery  of  Ley  den  jars  can  be  made 
to  give  out  an  electric  current,  and  this  current  will  affect 
a  magnetic  needle  in  the  same  way  that  a  battery  current 
will.  It  will  magnetize  steel.  If  passed  through  water,  it 
will  decompose  the  water  into  the  two  gases  oxygen  and 
hydrogen.  In  short,  a  current  from  an  electrical  machine 
or  a  Ley  den  jar  will  do  everything  that  a  current  from  an 
electric  battery  will  do.  Faraday  caused  the  Leyden  jar 
to  give  a  current  instead  of  a  spark  by  connecting  the  two 
metal  coatings  with  a  wet  string.  On  the  other  hand,  the 
discharge  from  a  powertul  electric  battery  willx  produce  a 
spark  and  affect  the  human  nerves  in  the  same  way  as  the 
discharge  from  the  electrical  machine.  The  same  effects 
may  be  obtained  from  one  as  from  the  other. 

In  the  discharge  from  the  machine,  a  small  quantity  of 
electricity  is  discharged  under  high  pressure,  as  water  may 
be  forced  through  a  small  opening  by  very  high  pressure. 

83 


THE  STORY  OF  GREAT  INVENTIONS 

The  voltaic  cell,  on  the  other  hand,  furnishes  a  large  quantity 
of  electricity  at  low  pressure,  as  a  street  may  be  flooded  by 
a  broken  water-main  though  the  pressure  is  low.  In  fact, 
the  quantity  of  electricity  required  to  decompose  a  grain 
of  water  is  equal  to  that  discharged  in  a  stroke  of  lightning, 
while  the  action  of  a  dilute  acid  on  the  one-hundredth  part 
of  an  ounce  of  zinc  in  a  battery  yields  electricity  sufficient 
for  a  powerful  thunder-storm. 

Many  tests  were  made,  and  the  result  was  a  convincing 
proof  that  electricity  is  the  same  whatever  its  source,  the 
different  effects  being  due  to  difference  in  pressure  and 
quantity.  "But  in  no  case,"  said  Faraday,  "not  even  in 
those  of  the  electric  eel  and  torpedo,  is  there  a  production 
of  electric  power  without  something  being  used  up  to  sup- 
ply it." 

Faraday's  professional  work  would  have  made  him 
wealthy.  In  one  year  he  made  £1000  ($5000),  and  the 
amount  would  have  increased  had  he  sold  his  services  at 
their  market  value.  But  then  there  would  have  been  no 
Faraday  the  discoverer.  The  world  would  have  had  to 
wait,  no  one  knows  how  long,  for  the  laying  of  the  founda- 
tions of  electrical  industries.  He  chose  to  give  up  wealth 
for  the  sake  of  discovery.  He  gave  up  professional  work 
with  the  exception  of  scientific  adviser  to  Trinity  House, 
the  body  which  has  charge  of  Great  Britain's  lighthouse 
service.  Nor  did  he  carry  his  discoveries  to  the  point  of 
practical  application.  As  soon  as  he  discovered  one  prin- 
ciple, he  set  out  in  pursuit  of  others,  leaving  the  practical 
application  to  the  future. 

Faraday  loved  the  beauty  of  nature.  The  sunset  he 

84 


FARADAY   AND   THE   FIRST   DYNAMO 

called  the  scenery  of  heaven.  He  saw  the  beauty  of  elec- 
tricity, which  he  said  lies  not  in  its  mystery,  but  in  the 
fact  that  it  is  under  law  and  within  the  control  of  the  human 
intellect. 

A  Wonderful  Law  of  Nature 

Not  long  after  Faraday  made  his  first  dynamo,  Robert 
Mayer,  a  physician  from  Germany,  was  making  a  voyage 
to  the  East  Indies  which  proved  to  be  a  voyage  of  discovery. 
He  had  sailed  as  the  ship's  physician,  and  after  some 
months  an  epidemic  broke  out  among  the  ship's  company. 
In  his  treatment  he  drew  blood  from  the  veins  of  the  arms. 
He  was  startled  to  see  bright-red  blood  issue  from  the  veins. 
He  might  almost  have  believed  that  he  had  opened  an  artery 
by  mistake.  It  was  soon  explained  to  him  by  a  physician 
who  had  lived  long  in  the  tropics  that  the  blood  in  the  veins 
of  the  natives,  and  of  foreigners  as  well,  in  the  tropics  is 
of  nearly  the  same  color  as  arterial  blood.  In  colder 
climates  the  venous  blood  is  much  darker  than  the  arte- 
rial. 

He  reasoned  upon  this  curious  fact  for  some  time,  and 
came  to  the  conclusion  that  the  human  body  does  not 
make  heat  out  of  nothing,  but  consumes  fuel.  The  fuel  is 
consumed  in  the  blood,  and  there  the  heat  is  produced.  In 
the  tropics  less  heat  is  needed,  less  fuel  is  consumed,  and 
therefore  there  is  less  change  in  the  color  of  the  blood. 

When  a  man  works  he  uses  up  fuel.  If  a  blacksmith 
heats  a  piece  of  iron  by  hammering,  the  heat  given  to  the 
iron  and  the  heat  produced  in  his  body  are  together  equal 
to  the  heat  of  the  fuel  consumed  in  his  blood.  The  work  a 

85 


THE  STORY  OF  GREAT  INVENTIONS 

man  does,  as  well  as  the  heat  of  his  body,  comes  from  the 
burning  of  the  fuel  in  his  blood. 

What  is  true  of  a  man  is  true  of  an  engine.  The  work 
the  engine  does,  as  well  as  the  heat  it  produces,  comes  from 
the  heat  of  the  fuel  in  the  furnace.  Mayer  found  that  one 
hundred  pounds  of  coal  in  a  good  working  engine  produces 
the  same  amount  of  heat  as  ninety-five  pounds  in  an  engine 
that  is  not  working.  In  the  working  engine  the  heat  of  the 
five  pounds  of  coal  is  used  up  in  the  work  of  running  the 
engine,  and  therefore  does  not  heat  the  engine.  Heat  that 
is  used  in  running  the  engine  is  no  longer  heat,  but  work. 
So  Mayer  said  the  heat  is  not  destroyed,  but  only  changed 
into  work.  He  said,  further,  that  the  work  of  running  the 
engine  may  be  changed  again  into  heat. 

Mayer's  theory  was  opposed  by  many  scientific  men  of 
Europe.  One  great  scientist  said  to  him  that  if  his  theory 
were  correct  water  could  be  warmed  by  shaking.  He  re- 
membered what  the  helmsman  had  remarked  to  him  on 
the  voyage  to  Java,  that  water  beaten  about  by  a  storm  is 
warmer  than  quiet  sea- water;  but  he  said  nothing.  He 
went  to  his  laboratory,  tried  the  experiment,  and  some 
weeks  later  returned,  exclaiming:  "It  is  so!  It  is  so!" 
He  had  warmed  water  simply  by  shaking  it. 

These  results  mean  that  work  or  energy  cannot  be  de- 
stroyed. Though  it  changes  form  in  many  ways,  it  is  never 
destroyed.  Neither  can  man  create  energy;  he  can  only 
direct  its  changes  as  the  engineer,  by  the  motion  of  his 
finger  in  opening  a  valve,  sets  the  locomotive  in  motion.  He 
does  not  move  the  locomotive.  He  directs  the  energy  al- 
ready in  the  steam. 

86 


FARADAY   AND   THE   FIRST   DYNAMO 

Since  the  time  of  Galileo,  men  had  caught  now  and  then 
a  glimpse  of  this  great  law..  Galileo  had  stated  his  law  of 
machines;  that,  when  a  machine  does  work,  a  man  or  a 
horse  or  some  other  power  does  an  equal  amount  of  work 
upon  the  machine.  Count  Rumford  had  performed  his  ex- 
periment with  the  cannon,  showing  that  heat  is  produced 
by  the  work  of  a  horse.  Davy  had  proved  that,  in  the 
voltaic  battery,  something  must  be  used  up  to  produce  the 
current — the  mere  contact  of  the  metals  is  not  sufficient. 
Faraday  had  said  that  in  no  case  is  there  a  production  of 
electrical  power  without  something  being  used  up  to  supply 
it.  Mayer  stated  clearly  this  law  of  energy  when  he  said 
that  energy  cannot  be  created  or  destroyed,  but  only 
changed  from  one  form  to  another. 

And  yet  inventors  have  not  learned  the  meaning  of  this 
law.  They  continue  trying  to  invent  perpetual  -  motion 
machines — machines  that  will  produce  work  from  nothing. 
This  is  what  a  perpetual-motion  machine  would  be  if  such 
a  machine  were  possible.  For  a  machine  without  friction  is 
impossible,  and  friction  means  wasted  work — work  changed 
into  heat.  A  machine  to  keep  itself  running  and  supply 
the  work  wasted  in  friction  must  produce  work  from  noth- 
ing. The  great  law  of  nature  is  that  you  cannot  get  some- 
thing for  nothing.  Whether  you  get  work,  heat,  electricity, 
or  light,  something  must  be  used  up  to  produce  it.  For 
whatever  you  get  out  of  a  machine  you  must  give  an  equiva- 
lent. This  law  cannot  be  evaded,  and  from  it  there  is  no 
appeal. 


Chapter  V 
GREAT   INVENTIONS  OF  THE  NINETEENTH  CENTURY 

THE  discoveries  of  Faraday  prepared  the  way  for  the 
great  Inventions  of  the  nineteenth  century.  By  the 
middle  of  the  century  men  knew  how  to  control  the  won- 
derful power  of  electricity.  They  did  not  know  what  elec- 
tricity is,  nor  do  we  know  to-day,  though  we  have  made 
some  progress  in  that  direction ;  but  to  control  it  and  make 
it  furnish  light,  heat,  and  power  was  more  important. 

Before  the  inventions  of  James  Watt  made  it  possible  to 
use  steam-power,  factories  were  built  near  falling  water,  so 
that  water-power  could  be  used.  But  the  steam-engine 
made  it  possible  to  build  great  factories  wherever  a  supply 
of  water  for  the  boilers  could  be  obtained.  Cities  were  built 
around  the  factories.  Cities  already  great  became  greater. 
With  the  growth  of  cities  the  need  of  a  new  means  of  pro- 
ducing light  and  power  made  itself  felt.  Electricity  prom- 
ised to  become  the  Hercules  that  should  perform  the  tasks 
of  the  modern  world. 

Discovery  gave  way  to  invention.  During  the  second 
half  of  the  nineteenth  century  many  great  inventions  were 
made  and  industries  were  developed,  while  discoveries  were 
few  until  near  the  close  of  the  century.  Within  this  period 

88 


NINETEENTH-CENTURY   INVENTIONS 

the  great  industries  which  characterize  our  modern  civiliza- 
tion, and  which  arose  out  of  the  discoveries  that  science  had 
made  in  the  centuries  preceding,  attained  a  high  degree  of 
development.  In  this  chapter  we  shall  trace  the  applica- 
tions of  some  of  the  discoveries  with  which  we  have  now 
become  familiar.  This  will  lead  us  into  the  field  of  electri- 
cal invention,  for  we  are  dealing  now  with  the  beginning 
of  the  world's  electrical  age. 

Electric  Batteries 

From  the  time  of  Volta  to  the  time  of  Faraday  the  only 
means  of  producing  an  electric  current  was  the  "  voltaic  bat- 
tery," so  called  in  honor  of  Volta.  The  voltaic  cell  is  the 
simplest  form  of  electric  battery.  In  this  cell  the  zinc  and 
copper  plates  are  placed  in  sulphuric  acid  diluted  with 
water.  As  the  acid  eats  the  zinc,  hydrogen  gas  is  formed. 
This  gas  collects  in  bubbles  on  the  copper  plate  and  weakens 
the  current.  The  aim  of  inventors  was  to  produce  a  steady 
current,  to  devise  a  battery  in  which  no  gas  would  collect 
on  the  copper  plate.  They  saw  the  need  of  a  battery  that 
would  give  out  a  current  of  unchanging  strength  until  the 
zinc  or  the  acid  was  used  up. 

The  first  real  improvement  in  the  battery  was  made  by 
Professor  Daniell,  of  King's  College,  London.  In  the  Daniell 
cell  the  zinc  plate  is  in  dilute  sulphuric  acid,  and  the  copper 
plate  is  in  a  solution  of  blue  vitriol  or  copper  sulphate. 
Professor  Danieil  separated  the  two  liquids  by  placing  one 
of  them  in  a  tube  formed  of  the  gullet  of  an  ox.  This  tube 
dipped  into  the  other  liquid.  The  hydrogen  gas,  as  it  was 

89 


THE  STORY  OF  GREAT  INVENTIONS 

formed  by  the  acid  acting  on  the  zinc,  could  go  through 
the  walls  of  the  tube,  but  was  stopped  by  the  copper  sul- 
phate, and  copper  was  deposited  on  the  copper  plate.  This 
copper  deposit  in  no  way  interfered  with  the  current,  so 
that  the  current  was  not  weakened  until  the  zinc  plate  or 
one  of  the  solutions  was  nearly  consumed.  A  cup  of  porous 
earthenware  is  now  used  in  Daniell  cells  to  separate  the 


FIG.    37 A    DANIELL    CELL 

liquids  (Fig.  37).  By  placing  crystals  of  blue  vitriol  in  the 
battery  jar,  the  solution  of  blue  vitriol  can  be  kept  up  to 
its  full  strength  for  a  very  long  time.  The  zinc  in  time  is 
consumed,  and  must  be  replaced. 

90 


NINETEENTH-CENTURY   INVENTIONS 


FIG.    38 A    GRAVITY    CELL 


In  the  gravity  cell  (Fig.  38) 
the  same  materials  are  used 
as  in  the  Daniell  cell  —  cop- 
per in  copper  sulphate,  and 
zinc  in  sulphuric  acid;  but 
there  is  no  porous  cup.  The 
solutions  are  kept  separate 
by  gravity,  the  heavy  cop- 
per sulphate  being  at  the 
bottom.  The  gravity  cell  has 
until  recently  been  extensive- 
ly used  in  telegraphy,  and 
continues  in  use  in  short-dis- 
tance telegraphy  and  in  au- 
tomatic block  signals.  The 

gravity  and  Daniell  cells  are  used  for  closed-circuit  work- 
that  is,  for  work  in  which  the  current  is  flowing  almost  con- 
stantly. 

The  Dry  Battery 

Another  important  improvement  was  the  invention  of 
the  dry  battery.  You  will  remember  that  the  first  battery, 
the  one  invented  by  Volta,  was  a  form  of  dry  battery ;  but 
it  was  a  very  feeble  battery  compared  with  the  dry  bat- 
teries now  in  use,  so  that  we  may  call  the  dry  battery  a 
new  invention.  The  dry  battery  is  falsely  named.  There 
can  be  no  battery  without  a  liquid.  In  the  dry  battery 
the  zinc  cup  forming  the  outside  of  the  cell  is  one  of  the 
plates  of  the  cell  (Fig.  39).  The  battery  appears  to  be  dry 
because  the  solution  of  sal  ammoniac  is  absorbed  by  blot- 
ting-paper or  other  porous  substance  in  contact  with  the 


THE  STORY  OF  GREAT  INVENTIONS 


zinc.  The  inner  plate  is  carbon,  and  this  is  surrounded  by 
powdered  carbon  and  manganese  dioxide — the  latter  to 
remove  the  hydrogen  gas  which  collects  on  the  carbon 
plate.  This  gas  weakens  the  current  when  the  circuit  has 
been  closed  for  a  short  time,  but  is  slowly  removed  when 
the  circuit  is  broken.  Thus  the  battery  is  said  to  "recover." 

The  dry  cell  will  give 


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* 

ous    substance  tr/'tA 
sal  ammoniac 


Zinc 


dioxide. 


a  strong  current,  but  for 
a  short  time  only.  It 
recovers,  however,  if  al- 
lowed to  rest.  It  can 
be  used,  therefore,  only 
in  "open-circuit"  work 
— such  as  door-bell  cir- 
cuits, and  some  forms  of 
fire  and  burglar  alarm. 
A  door -bell  circuit  is 
open  nearly  all  the  time, 
the  current  flowing  only 
while  the  button  is  being 
pressed.  Some  forms  of 
wet  battery  work  in  the 
same  way  as  the  dry  bat- 
tery, and  are  used  like- 
wise for  open  -  circuit 
work.  In  these  batteries  carbon  and  zinc  plates  in  a  so- 
lution of  sal  ammoniac  are  used,  the  same  materials  as  in 
the  dry  battery.  The  only  difference  is  that  in  the  dry 
battery  the  solution  is  absorbed  by  some  porous  substance 
and  the  battery  sealed  so  that  it  appears  to  be  dry, 

92 


FIG.  39 SHOWING    WHAT    IS  IN 

BATTERY 


A    DRY 


NINETEENTH-CENTURY   INVENTIONS 

The  Storage  Battery 

One  of  the  greatest  improvements  in  electric  batteries  is 
the  storage  battery.  A  simple  storage  battery  may  be 
made  by  placing  two  strips  of  lead  in  sulphuric  acid  diluted 
with  water  and  connecting  the  lead  strips  to  a  battery  of 
Daniell  cells  or  dry  cells.  In  a  short  time  one  of  the  lead 
strips  will  be  found  covered  with  a  red  coating.  The  sur- 
face of  this  lead  strip  is  no  longer  lead  but  an  oxide  of  lead, 
somewhat  like  the  rust  that  forms  on  iron.  If  the  lead  strips 
are  now  disconnected  from  the  other  battery  and  connected 
to  an  electric  bell,  the  bell  will  ring.  We  have  here  two 
plates,  one  of  lead  and  one  of  oxide  of  lead,  in  dilute  sul- 
phuric acid.  This  forms  a  storage  battery. 

The  first  storage  battery  was  made  of  two  sheets  of  lead 
rolled  together  and  kept  apart  by  a  strip  of  flannel.  The 
lead  strips  thus  separated  were  immersed  in  dilute  sulphuric 
acid.  A  current  from  another  battery  was  passed  through 
this  cell  for  a  long  time — first  in  one  direction,  then  in  the 
other.  This  roughened  the  surface  of  the  lead  plates,  so 
that  the  battery  would  hold  a  greater  charge.  The  battery 
was  then  charged  by  passing  a  current  through  it  in  one 
direction  only  for  a  considerable  length  of  time.  Feeble 
cells  were  used  for  charging.  It  took  days,  and  sometimes 
weeks,  to  charge  the  first  storage  batteries.  Then  the  stor- 
age battery  would  give  out  a  strong  current  lasting  for  a 
few  hours.  It  slowly  accumulated  energy  while  being 
charged,  and  then  gave  out  this  energy  rapidly  in  the  form 
of  a  strong  electric  current.  For  this  reason  the  storage 
battery  was  called  an  "accumulator." 

93 


THE  STORY  OF  GREAT  INVENTIONS 


While  charging  the  storage  cell  there  was  formed  on  the 
negative  plate  a  coating  of  soft  lead,  and  on  the  positive 
plate  a  coating  of  dark-brown  oxide  of  lead.  It  was  found 

better  to  apply  these  coat- 
ings to  the  lead  plates  be- 
fore making  up  the  battery. 
Later  it  was  found  that 
the  battery  would  hold  a 
still  greater  charge  if  the 
plates  were  made  in  the 
form  of  "grids"  (Fig.  40), 
and  the  cavities  filled  with 
the  active  material  —  the 
negative  with  spongy  lead, 
and  the  positive  with  dark- 
brown  lead  oxide.  Some 
excellent  commercial  stor- 
age batteries  are  made  from 
lead  plates  by  the  action  of 
an  electric  current,  very 
much  as  Plante  made  his 
batteries.  Fig.  41  shows 
one  of  these  plates. 


FIG.  4< 


-A  STORAGE   BATTERY,  SHOW- 
ING THE   "GRIDS" 


The  storage  battery  does 
not  store  up  electricity.  It 
produces  a  current  in  exactly  the  same  way  as  any  other 
battery — by  the  action  of  the  acid  on  the  plates.  When 
this  action  ceases  it  is  no  longer  a  battery,  though  it  may 
be  made  one  again  by  passing  a  current  through  it  in  the 
opposite  direction  from  that  which  it  gives  out.  In  this 

94 


NINETEENTH-CENTURY    INVENTIONS 


it  differs  from  the  voltaic  battery,  for  when  such  a  battery 
is  run  down  it  can  be  restored  only  by  adding  new  solution 
or  new  plates.  The  storage  battery  is  especially  useful  for 
"sparking"  in  gas  or  gasolene  motors. 

Edison  has  invented  a  storage  battery  that  will  do  as 
much  work  as  a  lead  battery  of  twice  its  weight.  Edison's 
battery  is  intended  especially  for  use  in  electric  automobiles. 
By  reducing  the  weight 
of  the  battery  which 
the  machine  must  car- 
ry the  weight  of  the 
truck  may  also  be  re- 
duced. In  the  Edison 
battery  the  positive 
plates  are  made  of  a 
grid  of  nickel  -  plated 
steel  containing  tubes 
filled  with  pure  nickel. 
The  negative  plate  con- 
sists of  a  nickel-plated 
steel  grid  containing  an 
oxide  of  iron  similar  to 
common  iron-rust. 

After  working  a  num- 
ber of  years  on  this  bat- 
tery and  making  nine 
thousand  experiments, 
Edison  thought  he  had 
it  perfected,  and  indeed 

,    .  FIG.    41 A     STORAGE  -  BATTERY     PLATE 

It  Was  a  great  improve-  MADE  FROM  A  SHEET  OF  LEAD 

7  95 


THE  STORY  OF  GREAT  INVENTIONS 

ment  over  the  storage  batteries  that  had  been  used  —  much 
lighter  and  cheaper,  and  more  successful  in  operation.  Two 
hundred  and  fifty  automobiles  were  equipped  with  it,  and  it 
proved  superior  to  lead  batteries  for  this  purpose.  But  it  was 
not  to  Edison's  liking.  He  threw  the  machinery,  worth  thou- 
sands of  dollars,  on  the  scrap-heap,  and  worked  on  for  six 
years.  He  had  then  produced  a  battery  as  much  better 
than  the  first  as  the  first  was  better  than  the  lead  battery, 
and  he  was  content  to  have  the  new  battery  placed  on  the 
market. 

The  Dynamo 

For  the  purpose  of  lighting  and  power  the  electric  bat- 
tery proved  too  costly.  Davy  produced  an  arc  light  with 
a  battery  of  four  thousand  cells.  The  arc  was  about  four 
inches  in  length  and  yielded  a  brilliant  light,  but  as  the 
cost  was  six  dollars  a  minute  it  was  not  thought  practical. 
Attempts  were  made  early  in  the  century  to  use  a  battery 
current  for  power,  but  they  failed  because  of  the  cost  and 
the  fact  that  no  good  working  motor  had  been  invented. 

Light  and  power  were  needed.  Electricity  could  supply 
both.  But  how  overcome  the  difficulty  of  cost,  and  produce 
an  electric  current  from  burning  coal  or  falling  water  ?  For 
answer  man  looked  to  the  great  discovery  of  Faraday  and 
his  "new  electrical  machine."  Inventors  in  Germany, 
France,  England,  Italy,  and  America  made  improvements 
until  from  the  disk  dynamo  of  Faraday  there  had  evolved 
the  modern  dynamo. 

Electroplating  and  the  telegraph  are  the  only  applica- 
tions of  the  electric  current  that  became  factors  in  the 

96 


NINETEENTH-CENTURY   INVENTIONS 


world's  industry  before  the  dynamo,  yet  in  long-distance 
telegraphy  and  in  electroplating  to-day  the  dynamo  is  used. 
Without  the  dynamo,  electric  lighting,  electric  power,  and 
electric  traction  as  developed  in  the  nineteenth  century 
would  have  been  impossible;  in  fact,  the  dynamo  with  the 
electric  motor  (which,  as  we 
shall  see,  is  only  a  dynamo 
reversed)  is  master  of  the 
field. 

The  way  had  been  pre- 
pared for  the  application 
of  Faraday's  discovery  by 
William  Sturgeon,  an  Eng- 
lishman, and  Joseph  Henry, 
an  American.  Sturgeon  dis- 
covered that  soft  iron  is 
more  quickly  magnetized 
than  steel,  and  found  that 
the  strength  of  an  electro- 
magnet can  be  greatly  in- 
creased by  making  the  core 
of  a  soft-iron  rod  and  bend- 


FIG'  42~ 


ELECTR°- 


ing  the  rod  into  the  form 

of  a  horseshoe  (Fig.  42).  The  iron  rod  was  coated  with 
sealing-wax  and  wound  with  a  single  layer  of  copper  wire, 
the  turns  of  wire  not  touching.  This  was  in  1825,  before 
Faraday  discovered  the  principle  of  the  dynamo. 

Professor  Henry  still  further  increased  the  strength  of 
the  electromagnet  by  covering  the  wire  with  silk,  which 
made  it  possible  to  wind  several  layers  of  wire  on  the  iron 

97 


THE  STORY  OF  GREAT  INVENTIONS 


FIG.  43 AN    ELECTROMAGNET    WITH    MANY   TURNS    OF    INSULATED    WIRE 

core,  and  many  times  the  length  of  wire  that  had  been 
used  by  Sturgeon.  Fig.  43  shows  such  a  magnet.  One  of 
Henry's  magnets  weighed  fifty-nine  and  a  half  pounds,  and 
would  hold  up  a  ton  of  iron.  Sturgeon  said:  " Professor 
Henry  has  produced  a  magnetic  force  which  completely 
eclipses  every  other  in  the  whole  annals  of  magnetism." 
With  Professor  Henry's  invention  the  electromagnet  was 
ready  for  use  in  the  dynamo.  Fig.  44  shows  a  strong 
electromagnet. 

A  moving  magnet  causes  a  current  to  flow  in  a  coil,  but 
a  magnet  at  rest  has  no  effect.  A  moving  magnet  is  equal 
to  a  battery.  In  Faraday's  experiments  a  current  was  in- 
duced in  a  coil  of  wire  by  moving  a  magnet  in  the  coil  or  by 

98 


\ 


NINETEENTH-CENTURY   INVENTIONS 


making  and  breaking  the  circuit  in  another  coil  wound  on 
the  same  iron  core.  A  current  was  induced  in  a  metal  disk 
by  revolving  it  between  the  poles  of  a  magnet.  In  every 
case  there  was  motion  in  a  magnetic  field,  or  the  field  itself 
was  changed.  A  changing  magnetic  field  is  equal  to  a 
moving  magnet.  What 
is  needed  to  induce  a 
current  in  a  coil,  whether 
it  be  in  a  dynamo,  an 
induction-coil,  or  a  trans- 
former, is  a  changing 
magnetic  field  about  the 
coil  or  motion  of  the  coil 
in  the  magnetic  field. 

If  fine  iron  filings  are 
sprinkled  over  the  poles 
of  a  magnet  the  filings 
arrange  themselves  in 
definite  lines.  This  is  a 
simple  experiment  which 
any  boy  can  try  for  him- 
self. Faraday  called  the 
lines  marked  out  by  the 
iron  filings  "lines  of 
force"  (the  lines  of  force 
of  a  horseshoe  magnet 
are  shown  in  Fig.  36), 

because  they  indicate  the  direction  -  in  which  the  mag- 
net pulls  a  piece  of  iron  —  that  is,  the  direction  of  the 
magnetic  force.  Now,  if  a  current  is  to  be  induced  in  a 

99 


FIG.    44 AN     ELECTROMAGNET      LIFTING 

TWELVE    TONS    OF    IRON 


THE  STORY  OF  GREAT  INVENTIONS 

wire,  the  wire  must  move  across  the  lines  of  force.  If 
the  wire  moves  along  the  lines  marked  out  by  the  iron 
filings,  there  will  be  no  current.  When  a  coil  rotates  be- 
tween the  poles  of  a  magnet,  the  wire  moves  across  the  lines 
of  force  and  a  current  is  induced  in  the  coil  if  the  circuit  is 
closed.  This  is  the  way  a  current  is  produced  in  a  dynamo. 
Faraday  produced  a  current  by  rotating  a  coil  between 
the  poles  of  a  steel  magnet.  He  made  a  number  of  such 
machines,  and  used  them  with  some  success  in  producing 
lights  for  lighthouses,  but  the  defects  of  these  machines 
were  so  great  that  the  lighting  of  a  city  or  the  development 
of  power  on  a  large  scale  was  impractical.  The  electro- 
magnet was  needed  to  solve  the  problem. 

Siemens'  Dynamo 

The  war  of  1866  between  Austria  and  Prussia  and  the 
certainty  of  a  coming  struggle  with  France  turned  the  at- 
tention of  German  inventors  to  the  use  of  electricity  in 
warfare.  Werner  von  Siemens,  an  artillery  officer,  was 
improving  an  exploding  device  for  mines.  An  electric  cur- 
rent was  needed  to  produce  a  spark  or  heat  a  wire  to  red- 
ness in  the  powder.  Faraday  had  used  a  coil  of  wire  turn- 
ing between  the  poles  of  a  steel  magnet  to  produce  a  current. 
In  England  a  coil  turning  between  the  poles  of  an  electro- 
magnet had  been  used,  but  the  electromagnet  received 
its  current  from  another  machine  in  which  a  steel  magnet 
was  used.  Siemens  found  that  the  steel  magnet  could  be 
dispensed  with,  and  that  a  coil  turning  between  the  poles 
of  an  electromagnet  could  furnish  the  current  for  the 

100 


NINETEENTH-CENTURY   INVENTIONS 

electromagnet.  Two  things  are  needed,  then,  to  make  a 
dynamo:  an  electromagnet  and  a  coil  to  turn  between 
the  poles  of  that  magnet.  The  rotating  coil,  which  usually 
contains  a  soft-iron  core,  is  called  the  "  armature."  The 
coil  will  furnish  current  for  the  magnet  and  some  to  spare; 
in  fact,  only  a  small  part  of  the  current  induced  in  the  coil 
is  needed  to  keep  the  magnet  up  to  its  full  strength,  and  the 
greater  part  of  the  current  may  be  used  for  lighting  or 


FIG.    45 — A    DYNAMO    WITH    SIEMENS     ARMATURE 
101 


THE  STORY  OF  GREAT  INVENTIONS 

power.  The  new  machine  was  named  by  its  inventor  ' '  the 
dynamo-electric  machine."  The  name  has  since  been  short- 
ened to  ''dynamo."  The  first  practical  problem  which  the 
dynamo  solved  was  the  construction  of  an  electric  explod- 
ing apparatus  without  the  use  of  steel  magnets  or  bat- 
teries. A  dynamo  with  Siemens'  armature  is  shown  in  Fig.  45 . 


FIG.    46 RING    ARMATURE 

In  his  first  enthusiasm  the  inventor  dreamed  of  great 
things  for  the  new  machine,  among  others  an  electric  street 
railway  in  Berlin.  But  the  dynamo  was  not  yet  ready. 
The  difficulty  was  the  heating  of  the  iron  core  of  the  arma- 
ture, caused  by  the  action  of  induced  currents.  There  are 
induced  currents  in  the  iron  core  as  well  as  in  the  coil,  and, 
for  the  same  reason,  the  coil  and  the  iron  core  within  it  are 
both  moving  in  a  magnetic  field.  These  little  currents  circling 


102 


NINETEENTH-CENTURY   INVENTIONS 


FIG.    47 FIRST     DYNAMO    PATENTED    IN    THE    UNITED    STATES 

Intended  to  be  used  for  killing  whales. 

Photo  by  Claudy. 

round  and  round  in  the  iron  core  produce  heat.  The  rapid 
changing  of  the  magnetism  of  the  iron  also  heats  the  iron. 
It  remained  for  Gramme,  in  France,  to  apply  the  proper 
rgmedy.  This  remedy  was  an  armature  in  which  the  coil 
was  wound  on  an  iron  ring,  invented  by  an  Italian,  Pacinotti. 
Gramme  applied  the  principle  discovered  by  Siemens  to 
Pacinotti' s  ring,  and  produced  the  first  practical  dynamo  for 
strong  currents.  This  was  in  1868.  A  ring  armature  is 
shown  in  Fig.  46.  The  first  dynamo  patented  in  the  United 
States  is  shown  in  Fig.  47.  This  dynamo  is  only  a  curiosity. 

103 


THE  STORY  OF  GREAT  INVENTIONS 


The  Drum  Armature 

An  improvement  in  the  Siemens  armature  was  made  four 
years  later  by  Von  Hefner- Alteneck,  an  engineer  in  the  em- 
ploy of  Siemens.  This  improvement  consisted  in  winding 
on  the  iron  core  a  number  of  coils  similar  to  the  one  coil  of 
the  Siemens  armature,  but  wound  in  different  directions. 
This  is  called  the  "drum  armature"  (Fig.  48).  The  heating 

of  the  core  is  prevented 
by  building  it  up  of  a 
number  of  thin  iron 
plates  insulated  from 
one  another  and  by  air- 
spaces within  the  core. 
The  insulation  prevents 
the  small  currents  from 
flowing  around  in  the 
core.  The  air  -  spaces 
serve  for  cooling.  The 
drum  armature  was  a 
great  improvement  over 
both  the  Siemens  and 
the  Gramme  armatures. 
With  the  Siemens  one- 
coil  armature  there  is  a  point  in  each  revolution  at 
which  there  is  no  current.  The  current,  therefore,  varies 
during  each  revolution  of  the  armature  from  zero  to  full 
strength.  In  the  Gramme  armature  only  half  the  wire, 
the  part  on  the  outside  of  the  ring,  receives  the  full 
effect  of  the  magnetic  field.  The  inner  half  is  practically 

104 


FIG.    48 A    DRUM    ARMATURE,    SHOWING 

HOW    AN    ARMATURE    OF    FOUR 
COILS    IS    WOUND 


NINETEENTH-CENTURY   INVENTIONS 

useless,  except  to  carry  the  current  which  is  generated  in 
the  outer  half.  Both  these  difficulties  are  avoided  in  the 
drum  armature.  The  dynamos  of  to-day  are  modifications 
of  the  two  kinds  invented  by  Siemens  and  Gramme.  Many 
special  forms  have  been  designed  for  special  kinds  of  work. 

Edison's  Compound- Wound  Dynamo 

Edison,  in  his  work  on  the  electric  light  and  the  electric 
railway,  made  some  important  improvements  in  the  dynamo. 
The  armature  of  a  dynamo  is  usually  turned  by  a  steam- 
engine.  Edison  found  that  much  power  was  wasted  in  the 
use  of  belts  to  connect  the  engine  and  the  dynamo.  He 
therefore  connected  the  engine  direct  to  the  dynamo, 
placing  the  armature  of  the  dynamo  on  the  shaft  of  the 
engine.  He  also  used  more  powerful  field  -  magnets  than 
had  been  used  before.  His  greatest  improvement,  how- 
ever, was  in  making  the  dynamo  self-regulating,  so  that 
the  dynamo  will  send  out  the  strength  of  current  that  is 
needed.  Such  a  dynamo  will  send  out  more  current  when 
more  lights  are  turned  on.  Whether  it  supplies  current 
for  one  light  or  a  thousand,  it  sends  out  just  the  current 
that  is  needed — no  more,  no  less.  It  will  do  this  if  no  hu- 
man being  is  near.  An  attendant  is  needed  only  to  keep 
the  machinery  well  oiled  and  see  that  each  part  is  in  work- 
ing order.  Edison  brought  about  this  improvement  by  his 
improved  method  of  winding.  This  method  is  known  as 
''compound  winding." 

To  understand  compound  winding  we  must  first  under- 
stand two  other  methods  of  winding.  In  the  series  wind- 

105 


THE  STORY  OF  GREAT  INVENTIONS 

ing  (Fig.  49),  all  the  current  generated  in  the  armature  flows 
through  the  coils  of  the  field-magnet.  There  is  only  one 
circuit.  The  same  current  flows  through  the  coils  of  the 


FIG.    49 A    SERIES-WOUND    DYNAMO 

magnet  and  through  the  outer  circuit,  which  may  contain 
lights  or  motors.  Such  a  dynamo  is  commonly  used  for 
arc  lights.  It  will  not  regulate  itself.  If  left  to  itself  it  will 
give  less  electrical  pressure  when  more  pressure  is  needed. 
It  requires  a  special  regulator. 

In  the  second  form  of  winding  the  current  is  divided  into 

106 


NINETEENTH-CENTURY   INVENTIONS 

two  branches.  One  branch  goes  through  the  coils  of  the 
field-magnet.  The  other  branch  goes  through  the  line  wire 
for  use  in  lights  or  motors.  This  is  called  the  "  shunt  wind- 
ing "  (Fig.  50) .  The  shunt-wound  dynamo  is  used  for  incan- 
descent lights.  It  also  requires  a  special  regulator,  for  if  left 


FIG.     50 A    SHUNT-WOUND    DYNAMO 

to  itself  it  gives  less  electrical  pressure  when  the  pressure 
should  be  kept  the  same. 

The  compound  winding  (Fig.  51),  which  was  first  used  by 
Edison,  is  a  combination  of  the  series  and  shunt  windings. 

107 


THE  STORY  OF  GREAT  INVENTIONS 


FIG.    51 A    COMPOUND-WOUND    DYNAMO 

The  current  is  divided  into  two  branches.  One  branch  goes 
only  through  the  field-coils.  The  other  branch  goes  through 
additional  coils  which  are  wound  on  the  field-magnet,  and 
also  through  the  external  circuit.  Such  a  dynamo  can  be 
made  self-regulating,  so  that  it  will  give  always  the  same 
electrical  pressure  whatever  the  number  of  lamps  or  motors 
thrown  into  the  circuit.  In  maintaining  always  the  same 
pressure  it  of  course  supplies  more  or  less  current,  accord- 
ing to  the  amount  of  current  that  is  needed.  This  is  clear 
if  we  compare  the  flow  of  electric  current  with  the  flow  of 
water.  Open,  a  water-faucet  and  notice  how  fast  the  water 
flows.  Then  open  several  other  faucets  connected  with  the 
same  water-pipe.  Probably  the  water  will  not  flow  so  fast 
from  the  first  faucet.  That  is  because  the  pressure  has 
been  lowered  by  the  flow  of  water  from  the  other  faucets. 
If  we  could  make  the  water  adjust  its  own  pressure  and 
keep  the  pressure  always  the  same,  then  the  water  would 
always  flow  at  the  same  rate  through  a  faucet,  no  matter 

108 


FIG.    52 ONE    OF    EDISON'S    FIRST    DYNAMOS 

Permission  of  Association  of  Edison  Illuminating  Companies. 


THE  STORY  OF  GREAT  INVENTIONS 

how  many  other  faucets  were  opened.  This  is  what  hap- 
pens in  the  Edison  compound-wound  dynamo.  Turn  on 
one  1 6-candle-power  carbon  lamp.  It  takes  about  half  an 
ampere  of  current.  Turn  on  a  hundred  lamps  connected 
to  the  same  wires,  and  the  dynamo  of  its  own  accord  keeps 
the  pressure  the  same,  and  supplies  fifty  amperes,  or  half 


FIG.    53 A  DYNAMO   MOUNTED  ON   THE   TRUCK  OF  A   RAILWAY  CAR 

The  dynamo  furnishes  current  for  the  electric  lights  in  the  car.     When 
the  train  is  not  running  the  current  is  furnished  by  a  storage  battery. 

an  ampere  for  each  lamp.  With  this  invention  of  Edison 
the  dynamo  was  practically  complete,  and  ready  to  furnish 
current  for  any  purpose  for  which  current  might  be  needed. 
Fig.  52  shows  one  of  Edison's  first  dynamos.  Fig.  53  shows 
a  dynamo  used  for  lighting  a  railway  coach. 

no 


NINETEENTH-CENTURY   INVENTIONS 

Electric  Power 

It  has  been  said  that  the  nineteenth  century  was  the  age 
of  steam,  but  the  twentieth  will  be  the  age  of  electricity. 
Before  the  end  of  the  nineteenth  century,  however,  electric 
power  had  become  a  reality,  and  there  remained  only  de- 
velopment along  practical  lines. 

We  must  turn  to  Oersted,  Ampere,  and  Faraday  to  find 
the  beginning  of  electric  power.  In  Oersted's  experiment, 
motion  of  a  magnet  was  produced  by  an  electric  current. 
Ampere  found  that  electric  currents  attract  or  repel  each 
other,  and  this  because  of  their  magnetic  action.  Faraday 
found  that  one  pole  of  a  magnet  will  spin  round  a  wire 
through  which  a  current  is  flowing.  Here  was  motion  pro- 
duced by  an  electric  current.  These  great  scientists  dis- 
covered the  principles  that  were  applied  later  by  inventors 
in  the  electric  motor. 

A  number  of  motors  were  invented  in  the  early  years  of 
the  century,  but  they  were  of  no  practical  use.  It  was  not 
until  after  the  invention  of  the  Gramme  and  Siemens 
dynamos  that  a  practical  motor  was  possible.  It  was  found 
that  one  of  these  dynamos  would  run  as  a  motor  if  a  current 
were  sent  through  the  coils  of  the  armature  and  the  field- 
magnet;  in  fact,  the  current  from  one  dynamo  may  be 
made  to  run  another  similar  machine  as  a  motor.  Thus 
the  dynamo  is  said  to  be  reversible.  If  the  armature  is 
turned  by  a  steam-engine  or  some  other  power,  a  current 
is  produced.  If  a  current  is  sent  through  the  coils,  the 
armature  turns  and  does  work.  If  the  machine  is  used  to 
supply  an  electric  current,  it  is  a  dynamo.  If  used  to  do 

8  in 


THE  STORY  OF  GREAT  INVENTIONS 

work — as,  for  example,  to  propel  a  street -car  and  for  that 
purpose  receives  a  current — it  is  a  motor.  The  same  ma- 
chine may  be  used  for  either  purpose.  In  practice  there  are 
some  differences  in  the  winding  of  the  coils  of  dynamos  and 
motors,  yet  any  dynamo  can  be  used  as  a  motor  and  any 
motor  can  be  used  as  a  dynamo.  This  discovery  made  it 
possible  to  transmit  power  to  a  distance  with  little  waste 
as  well  as  to  divide  the  power  easily.  The  current  from 
one  large  dynamo  may  light  streets  and  houses,  and  at  the 
same  time  run  a  number  of  motors  in  factories  or  street- 
cars at  great  distances  apart.  A  central-station  dynamo 
may  run  the  motors  that  propel  hundreds  of  street-cars. 
Dynamos  at  Niagara  furnish  current  for  motors  in  Buffalo 
and  other  cities.  One  great  scientist,  who  no  doubt  fore- 
saw the  wonders  of  electricity  which  we  know  so  well 
to-day,  said  that  the  greatest  discovery  of  the  nineteenth 
century  was  that  the  Gramme  machine  is  reversible. 

The  First  Electric  Railway 

The  electric  railway  was  made  possible  by  the  invention 
of  the  dynamo  and  the  discovery  that  the  dynamo  is  re- 
versible. At  the  Industrial  Exposition  in  Berlin  in  1879 
there  was  exhibited  the  first  practical  electric  locomotive, 
the  invention  of  Doctor  Siemens.  The  locomotive  and  its 
passenger-coach  were  absurdly  small.  The  track  was  cir- 
cular, and  about  one  thousand  feet  in  length.  This  diminu- 
tive railway  was  referred  to  by  an  American  magazine  as 
"Siemens'  electrical  merry-go-round."  But  the  electrical 
merry-go-round  aroused  great  interest  because  of  the  pos- 
sibilities it  represented  (Fig.  54). 

112 


THE  STORY  OF  GREAT  INVENTIONS 

The  current  was  generated  by  a  dynamo  in  Machinery 
Hall,  this  dynamo  being  run  by  a  steam-engine.  An  exact- 
ly similar  dynamo  mounted  on  wheels  formed  the  locomotive. 
The  current  from  the  dynamo  in  Machinery  Hall  was  used 
to  run  the  other  as  a  motor  and  so  propel  the  car.  The 
rails  served  to  conduct  the  current.  A  third  rail  in  the 
middle  of  the  track  was  connected  to  one  pole  of  the  dynamo 
and  the  two  outer  rails  to  the  other  pole.  A  small  trolley 
wheel  made  contact  with  the  third  rail.  The  rails  were  not 
insulated,  but  it  was  found  that  the  leakage  current  was 
very  small,  even  when  the  ground  was  wet. 

The  success  of  this  experiment  aroused  great  interest, 
not  only  in  Germany,  but  in  Europe  and  America.  America's 
greatest  inventor,  Edison,  took  up  the  problem.  Edison  em- 
ployed no  trolley  line  or  third  rail,  but  only  the  two  rails  of 
the  track  as  conductors,  sending  the  current  out  through  one 
rail  and  back  through  the  other.  Of  course,  this  meant  that 
the  wheels  must  be  insulated,  so  that  the  current  could  flow 
from  one  rail  to  the  other  only  through  the  coils  of  the  motor. 

As  in  Siemens'  experiment,  the  motor  was  of  the  same 
construction  as  the  dynamo.  The  rails  were  not  insulated, 
and  it  was  found  that,  even  when  the  track  was  wet,  the 
loss  of  electric  current  was  not  more  than  5  per  cent.  Edison 
found  that  he  could  realize  in  his  motor  70  per  cent,  of  the 
power  applied  to  the  dynamo,  whereas  the  German  inventor 
was  able  to  realize  only  60  per  cent.  The  improvement  was 
largely  due  to  the  improved  winding.  Edison  was  the  first 
to  use  in  practical  work  the  compound-wound  dynamo,  and 
this  was  done  in  connection  with  his  electric  railway.  Fig. 
55  shows  Edison's  first  electric  locomotive. 

114 


THE  STORY  OF  GREAT  INVENTIONS 

The  question  of  gearing  was  a  troublesome  one.  The 
armature  shaft  of  the  motor  was  at  first  connected  by 
friction  gearing  to  the  axle  of  two  wheels  of  the  locomotive. 
Later  a  belt  and  pulleys  were  used.  An  idler  pulley  was 
used  to  tighten  the  belt.  When  the  motor  was  started  and 
the  belt  quickly  tightened  the  armature  was  burned  out. 
This  happened  a  number  of  times.  Then  Mr.  Edison  brought 
out  from  the  laboratory  a  number  of  resistance  -  boxes, 
placed  them  on  the  locomotive,  and  connected  them  in 
series  with  the  armature.  These  resistances  would  permit 
only  a  small  current  to  flow  through  the  motor  as  it  was 
starting,  and  so  prevent  the  burning-out  of  the  armature 
coils.  The  locomotive  was  started  with  the  resistance-boxes 
in  circuit,  and  after  gaining  some  speed  the  operator  would 
plug  the  various  boxes  out  of  circuit,  and  in  that  way  in- 
crease the  speed.  When  the  motor  is  running  there  is  a 
back-pressure,  or  a  pressure  that  would  cause  a  current  to 
flow  in  the  opposite  direction  from  that  which  is  running 
the  motor.  Because  of  this  back  -  pressure  the  current 
which  actually  flows  through  the  motor  is  small,  and  the 
resistance-boxes  may  be  safely  taken  out  of  the  circuit. 
Finding  the  resistance  -  boxes  scattered  about  under  the 
seats  and  on  the  platform  as  they  were  a  nuisance,  Mr.  Edison 
threw  them  aside,  and  used  some  coils  of  wire  wound  on  the 
motor  field-magnet  which  could  be  plugged  out  of  the  circuit 
in  the  same  way  as  the  resistance -boxes.  This  device  of  Edi- 
son's was  the  origin  of  the  controller,  though  in  the  controller 
now  used  on  street-cars  not  only  is  the  resistance  cut  out  as 
the  speed  of  the  car  increases,  but  the  electrical  connections 
of  the  motor  are  changed  in  such  a  way  as  to  increase  its 

116 


THE  STORY  OF  GREAT  INVENTIONS 

speed  gradually.     Fig.  56  shows  Edison's  first  passenger  loco- 
motive. 

The  news  of  the  little  electric  railway  at  the  Industrial 
Exposition  in  Berlin  was  soon  noised  abroad,  and  the  Ger- 
man inventor  received  inquiries  from  all  parts  of  the  world, 
indicating  that  efforts  would  be  made  in  other  countries 
to  develop  practical  electrical  railways.  The  firm  of  Sie- 
mens &  Halske  therefore  determined  to  build  a  line  for 
actual  traffic,  not  for  profit,  but  that  Germany  might  have 
the  honor  of  building  the  first  practical  electric  railway.  The 
line  was  built  between  Berlin  and  Lichterfelde,  a  distance 
of  about  one  and  a  half  miles.  A  horse-car  seating  twenty- 
six  persons  was  pressed  into  service.  A  motor  was  mounted 
between  the  axles,  and  a  central- station  dynamo  exactly 
like  the  motor  was  installed.  As  in  Edison's  experimental 
railway,  the  two  rails  of  the  track  were  used  to  carry  the 
current.  This  electric  line  replaced  an  omnibus  line,  and 
was  immediately  used  for  regular  traffic,  and  thus  the  electric 
railway  was  launched  upon  its  remarkable  career.  The  first 
electric  car  used  for  commercial  service  is  shown  in  Fig.  57. 

Electric  Lighting 

From  the  time  when  the  night-watchman  carried  a 
lantern  to  the  time  of  brilliantly  lighted  streets  was  less 
than  a  century.  It  was  a  time  when  the  rapid  growth  of 
railways  and  commerce  brought  about  a  rapid  growth  of 
cities,  and  with  the  growth  of  cities  the  need  of  illumina- 
tion. Factories  must  run  at  night  to  meet  the  world's  de- 
mands. Commerce  cannot  stop  when  the  sun  sets.  The 
centres  of  commerce  must  have  light. 

118 


NINETEENTH-CENTURY   INVENTIONS 

During  this  time  scientists  were  at  work  in  their  labora- 
tories developing  means  for  producing  a  high  vacuum.  They 
were  able  to  pump  the  air  out  of  a  glass  bulb  until  less  than 
a  millionth  part  of  the  air  remained.  They  little  dreamed 
that  there  was  any  connection  between  the  high  vacuum 
and  the  problem  of  lighting.  Discoverers  were  at  work 


FIG.     57 FIRST    COMMERCIAL    ELECTRIC    RAILWAY 

An   old   horse-car   converted   into   an   electric  car. 

bringing  to  light  the  principles  now  utilized  in  the  dynamo. 
In  the  fulness  of  time  these  factors  were  brought  together 
to  produce  an  efficient  system  of  lighting. 

For  a  time  gas  replaced  the  lantern  of  the  night-watchman, 
only  to  yield  the  greater  portion  of  the  field  to  its  rival, 
electricity. 

119 


THE  STORY  OF  GREAT  INVENTIONS 

The  first  efforts  were  in  the  direction  of  the  arc  light. 
From  the  earliest  times  the  light  given  out  by  an  electric 
spark  had  been  observed.  It  was  the  aim  of  inventors  to 
produce  a  continuous  spark  that  should  give  out  a  brilliant 
light.  It  was  thought  for  a  time  that  the  electric  battery 
would  solve  the  problem,  but  the  cost  of  the  battery  cur- 
rent was  too  great.  Again  we  are  indebted  to  Faraday,  for 
it  was  the  dynamo  that  made  electric  lighting  possible. 

An  arc  light  is  produced  by  an  electric  current  flowing 
across  a  gap  between  two  sticks  of  carbon.  The  air  offers 
very  great  resistance  to  the  flow  of  electric  current  across 
this  gap.  Now  whenever  an  electric  current  flows  through 
something  which  resists  its  flow,  heat  is  produced.  The 
high  resistance  of  the  air-gap  causes  such  intense  heat  that 
the  tips  of  the  carbons  become  white  hot  and  give  out  a 
brilliant  light.  If  examined  through  a  smoked  glass  a  beau- 
tiful blue  arc  of  carbon  vapor  may  be  seen  between  the 
carbon  tips.  If  the  current  flows  in  one  direction  only, 
one  of  the  carbons,  the  positive,  becomes  hotter  and  brighter 
than  the  other. 

In  1878  the  streets  of  Paris  were  lighted  with  the  "Jab- 
lochkoff  candle,"  a  form  of  arc  light  supplied  with  current 
by  the  Gramme  machine.  In  the  same  year  the  Brush 
system  of  arc  lighting  was  given  to  the  public.  This  was 
the  beginning  of  our  present  system  of  arc  lighting. 

The  electric  arc  is  suitable  for  lighting  streets  and  for 
large  buildings,  but  cannot  be  used  for  lighting  houses. 
The  light  is  too  intense.  One  arc  would  furnish  enough 
light  for  a  number  of  houses  if  the  light  could  be  divided 
So  that  there  might  be  just  the  right  amount  of  light  in 

120 


NINETEENTH-CENTURY   INVENTIONS 

each  room.  But  this  is  impossible  with  the  electric  arc. 
The  Edison  system  of  incandescent  lighting  was  required  to 
solve  the  problem  of  lighting  houses  by  electricity. 

In  1880  the  Edison  system  was  brought  out  for  commercial 
use.  Edison's  problem  was  to  produce  a  light  that  could 
be  divided  into  a  number  of  small  lights,  and  one  that 
would  require  less  attention  than  the  arc  light.  He  tried 
passing  a  current  through  platinum  wire  enclosed  in  a 
vacuum.  This  gave  a  fairly  good  light,  but  was  not  wholly 
satisfactory.  He  sat  one  night  thinking  about  the  problem, 
unconsciously  fingering  a  bit  of  lampblack  mixed  with  tar 
which  he  had  used  in  his  telephone.  Not  thinking  what  he 
was  doing,  he  rolled  this  mixture  of  tar  and  lampblack  into 
a  thread.  Then  he  noticed  what  he  had  done,  and  the 
thought  occurred  to  him:  ''Why  not  pass  an  electric  cur- 
rent through  this  thread  of  carbon?"  He  tried  it.  A  faint 
glow  was  the  result.  He  felt  that  he  was  on  the  right  track. 
A  piece  of  cotton  thread  must  be  heated  in  a  furnace  in  an 
iron  mold,  which  would  prevent  the  thread  from  burning 
by  keeping  out  the  air.  Then  all  the  other  elements  that 
were  in  the  thread  would  be  driven  out  and  only  the  carbon 
remain.  For  three  days  he  worked  without  sleep  to  pre- 
pare this  carbon  filament.  At  the  end  of  two  days  he  suc- 
ceeded in  getting  a  perfect  filament,  but  when  he  attempted 
to  seal  it  in  the  glass  bulb  it  broke.  He  patiently  worked 
another  day,  and  was  rewarded  by  securing  a  good  carbon 
filament  sealed  in  a  glass  globe.  He  pumped  the  air  out  of 
this  globe,  sealed  it,  and  sent  a  current  through  the  carbon 
thread.  He  tried  a  weak  current  at  first.  There  was  a 
faint  glow.  He  increased  the  current.  The  thread  glowed 

121 


NINETEENTH-CENTURY   INVENTIONS 

more  brightly.  He  continued  to  increase  the  current  until 
the  slender  thread  of  carbon,  which  would  crumble  at  a 
touch,  was  carrying  a  current  that  would  melt  a  wire  of 
platinum  strong  enough  to  support  a  weight  of  several 
pounds.  The  carbon  gave  a  bright  light.  He  had  found 
a  means  of  causing  the  electric  current  to  furnish  a  large 
number  of  small  lights.  Fig.  58  is  an  excellent  photograph 


Copyright,  1904.  by   William  J.  Hammer 

FIG.  59 — EDISON'S  FAMOUS  HORSESHOE  PAPER-FILAMENT  LAMP  OF  1870 

of  Edison  at  work  in  his  laboratory.  Fig.  59  shows  some  of 
Edison's  first  incandescent  lamps.  He  next  set  out  in 
search  of  the  best  kind  of  carbon  for  the  purpose.  He  car- 
bonized paper  and  wood  of  various  kinds — in  fact,  every- 
thing he  could  find  that  would  yield  a  carbon  filament.  He 
tried  the  fibres  of  a  Japanese  fan  made  of  bamboo,  and 
found  that  this  gave  a  better  light  than  anything  he  had 
tried  before.  He  then  began  the  search  for  the  best  kind 

123 


THE  STORY  OF  GREAT  INVENTIONS 

of  bamboo.  He  learned  that  there  are  about  twelve  hun- 
dred varieties  of  bamboo.  He  must  have  a  sample  of  every 
variety.  He  sent  men  into  every  part  of  the  world  where 
bamboo  grows.  One  man  travelled  thirty  thousand  miles 
and  had  many  encounters  with  wild  beasts  in  his  search  for 
the  samples  of  bamboo.  At  last  a  Japanese  bamboo  was 
found  that  was  better  than  any  other.  The  search  for  the 
carbon  fibre  had  cost  about  a  hundred  thousand  dollars. 
Later  it  was  found  that  a  "squirted  filament"  could  be 
made  that  worked  as  well  as  the  bamboo  fibre.  This  was 
made  by  dissolving  cotton  wool  in  a  certain  solution,  and 
then  squirting  this  solution  through  a  small  hole  into  a 
small  tank  containing  alcohol.  The  alcohol  causes  the  sub- 
stance to  set  and  harden,  and  thus  forms  a  carbon  thread 
the  size  of  the  hole.  Fig.  60  shows  the  first  commercial 
electric -lighting  plant,  which  was  installed  on  the  steamship 
Columbia  in  1880. 

The  carbon  thread  in  the  incandescent  light  is  heated  to 
a  white  heat,  and  because  it  is  so  heated  it  gives  out  light. 
In  air  such  a  tiny  thread  of  white-hot  carbon  would  burn 
in  a  fraction  of  a  second.  The  carbon  must  be  in  a  vacuum, 
and  so  the  air  is  pumped  out  of  the  light  bulb  with  a  special 
kind  of  air-pump  invented  not  long  before  Edison  began 
his  work  on  the  electric  light.  This  pump  is  capable 
of  taking  out  practically  all  the  air  that  was  in  the  bulb. 
Perhaps  a  millionth  part  of  the  original  air  remains. 

A  great  invention  is  never  completed  by  one  man.  It 
was  to  be  expected  that  the  electric  light  would  be  im- 
proved. A  number  of  kinds  of  incandescent  light  have  been 
devised,  using  different  kinds  of  filaments  and  adapted  to 

124 


NINETEENTH-CENTURY   INVENTIONS 


FIG.  60 FIRST  COMMERCIAL  EDISON  ELECTRIC-LIGHTING  PLANT;  INSTALLED 

ON    THE    STEAMSHIP    "  COLUMBIA  "    IN    MAY,     l88o 

a  variety  of  uses.  The  original  Edison  carbon  lamp,  how- 
ever, continues  in  use,  being  better  adapted  to  certain  pur- 
poses than  the  newer  forms. 

The  mercury  vapor  light  deserves  mention  as  a  special 
form  of  arc  light.  In  the  ordinary  arc  light  the  arc  is 
formed  of  carbon  vapor,  and  the  light  is  given  out  from  the 
tips  of  the  white-hot  carbons.  In  the  mercury  vapor  light 
the  light  is  given  out  from  the  mercury  vapor  which  forms 
the  arc.  This  arc  may  be  of  any  desired  length,  and  yields 
a  soft,  bluish-white  light  which  is  a  near  approach  to  day- 
light. 

125 


THE  STORY  OF  GREAT  INVENTIONS 

The  Telegraph 

The  need  of  some  means  of  giving  signals  at  a  distance 
was  early  felt  in  the  art  of  war.  Flag  signals  such  as  are 
now  used  by  the  armies  and  navies  of  the  world  were  intro- 
duced in  the  middle  of  the  seventeenth  century  by  the 
Duke  of  York,  admiral  of  the  English  fleet,  who  afterward 
became  James  II.  of  England.  Other  methods  of  com- 
municating at  a  distance  were  devised  from  time  to  time, 
but  the  distance  was  only  that  at  which  a  signal  could  be 
seen  or  a  sound  heard.  No  means  of  communicating  over 
very  long  distances  was  possible  until  the  magnetic  action 
of  an  electric  current  was  discovered.  When  Oersted's  dis- 
covery was  made  known  men  began  to  think  of  signalling  to 
a  distance  by  means  of  the  action  of  an  electric  current  on 
a  magnetic  needle.  A  current  may  be  sent  over  a  very 
long  wire,  and  it  will  deflect  a  magnetic  needle  at  the  other 
end.  The  movements  of  the  needle  may  be  controlled  by 
opening  and  closing  the  circuit,  and  a  system  of  signals  or 
an  alphabet  may  be  arranged.  A  number  of  needle  tele- 
graphs were  invented,  but  they  were  too  slow  in  action. 
Two  other  great  inventions  were  needed  to  prepare  the 
way  for  the  telegraph.  One  was  the  electromagnet  in  the 
form  developed  by  Professor  Henry,  a  horseshoe  magnet 
with  many  turns  of  silk-covered  wire  around  the  soft-iron 
core,  so  that  a  very  feeble  current  will  produce  a  magnet 
strong  enough  to  move  an  armature  of  soft  iron.  The  mag- 
net has  this  strength  because  the  current  flows  so  many 
times  around  the  iron  core.  Another  need  was  that  of  a 
battery  that  could  be  depended  on  to  give  a  constant  cur- 

126 


NINETEENTH-CENTURY   INVENTIONS 

rent  for  a  considerable  length  of  time.     This  need  was  met 
by  the  Daniell  cell. 

The  electromagnet  made  the  telegraph  possible.  The 
locomotive  made  it  a  necessity.  Without  the  telegraph  it 
would  be  impossible  to  control  a  railway  system  from  a 
central  office.  A  train  after  leaving  the  central  station 
would  be  like  a  ship  at  sea  before  the  invention  of  the  wire- 
less telegraph.  Nothing  could  be  known  of  its  movements 
until  it  returned.  The  need  of  a  telegraph  was  keenly  felt 
in  America  when  the  new  republic  was  extended  to  the 
Pacific  Coast.  An  English  statesman  said,  after  the  United 
States  acquired  California,  that  this  marked  the  end  of  the 
great  American  Republic,  for  a  people  spread  over  such  a 
vast  area  and  separated  by  such  natural  barriers  could 
not  hold  together.  He  did  not  know  that  the  iron  wire 
of  the  telegraph  would  bind  the  new  nation  firmly  to- 
gether. 

The  Morse  telegraph  system  now  in  use  throughout  the 
civilized  world  was  made  possible  by  the  work  of  Sturgeon 
and  Henry.  Sturgeon's  electromagnet  might  have  been 
used  for  telegraphy  through  very  short  distances,  but 
Henry's  magnet,  with  its  coils  of  many  turns  of  insulated 
wire,  was  needed  for  long-distance  signalling.  In  one  of 
the  rooms  of  the  Albany  Academy,  Professor  Henry  caused 
an  electromagnet  to  sound  a  bell  when  the  current  was 
transmitted  through  more  than  a  mile  of  wire.  This  might 
be  called  the  first  electromagnetic  telegraph.  But  the  ap- 
plication to  actual  practice  was  made  by  Morse,  and  the 
man  who  first  makes  the  practical  application  of  a  prin- 
ciple is  the  true  inventor. 

9  127 


THE  STORY  OF  GREAT  INVENTIONS 

In  1832,  on  board  the  packet-ship  Sully,  Samuel  F.  B. 
Morse,  an  American  artist,  forty-one  years  of  age,  was  re- 
turning from  Europe.  In  conversation  a  Doctor  Jackson 
referred  to  the  electrical  experiments  of  Ampere,  which  he 
had  witnessed  while  in  Europe,  and,  in  reply  to  a  question, 
said  that  electricity  passes  instantaneously  over  any  known 
length  of  wire.  The  thought  of  transmitting  words  by 
means  of  the  electric  current  at  once  took  possession  of  the 
artist's  mind.  After  many  days  and  sleepless  nights  he 
showed  to  friends  on  board  the  drawings  and  notes  he  had 
made  of  a  recording  telegraph. 

In  New  York,  in  a  room  provided  by  his  brothers,  he 
gave  himself  up  to  the  working-out  of  his  idea,  sleeping 
little  and  eating  the  simplest  food.  Receiving  an  appoint- 
ment as  professor  in  the  University  of  the  City  of  New 
York,  he  moved  to  one  of  the  buildings  of  that  university 
and  continued  his  experiments  in  extreme  poverty,  and  at 
times  facing  starvation,  as  his  salary  depended  on  the  tui- 
tion fees  of  his  pupils. 

A  story  told  by  one  of  his  pupils  describes  his  condition 
at  the  time. 

"I  engaged  to  become  one  of  Morse's  pupils.  He  had 
three  others.  I  soon  found  that  the  professor  had  little 
patronage.  I  paid  my  fifty  dollars;  that  settled  one  quar- 
ter's tuition.  I  remember,  when  the  second  was  due,  my 
remittance  from  home  did  not  come  as  expected,  and  one 
day  the  professor  came  in  and  said,  courteously: 

14  *  Well,  Strother,  my  boy,  how  are  we  off  for  money?' 
"Why,  professor,  I  am  sorry  to  say  I  have  been  disap- 
pointed;  but  I  expect  a  remittance  next  week.' 

128 


NINETEENTH-CENTURY   INVENTIONS 

"'Next  week!'  he  repeated,  sadly;  'I  shall  be  dead  by 
that  time.' 

'"Dead,  sir?' 

"'Yes;   dead  by  starvation!' 

"I  was  distressed  and  astonished.  I  said,  hurriedly: 
'Would  ten  dollars  be  of  any  service?' 

"'Ten  dollars  would  save  my  life;  that  is  all  it  would 
do.'" 

The  money  was  paid,  all  the  student  had,  and  the  two 
dined  together.  It  was  Morse's  first  meal  in  twenty-four 
hours. 

The  Morse  telegraph  sounder   (Fig,   61)   consists  of  an 


FIG.    6l A    TELEGRAPH    SOUNDER 


electromagnet  and  a  soft-iron  armature.  When  no  current 
is  flowing  the  armature  is  held  away  from  the  magnet  by  a 
spring.  When  the  circuit  is  closed  a  current  flows  through 

129 


THE  STORY  OF  GREAT  INVENTIONS 

the  coils  of  the  magnet  and  the  armature  is  attracted,  caus- 
ing a  click.  When  the  circuit  is  broken  the  spring  pulls  the 
armature  away  from  the  magnet,  causing  another  click. 
The  circuit  is  made  and  broken  by  means  of  a  key  at  the 
other  end  of  the  line.  In  Morse's  first  instrument  (Fig.  62) 
the  armature  carried  a  pen,  which  was  drawn  across  a  rib- 
bon of  paper  when  the  armature  was  attracted  by  the  magnet. 
If  the  pen  was  held  by  the  magnet  for  a  very  short  time,  a 
dot  was  made ;  if  for  a  longer  time,  a  dash.  The  pen  was 
soon  discarded,  and  the  message  taken  by  sound  only. 
The  Morse  alphabet  now  in  use  was  devised  by  a  Mr.  Vail, 
who  assisted  Morse  in  developing  the  telegraph.  The 
thought  occurred  to  Mr.  Vail  that  he  could  get  help  from 
a  printing-office  in  deciding  the  combinations  of  dots  and 
dashes  that  should  be  used  for  the  different  letters.  The 
letters  requiring  the  largest  spaces  in  the  type-cases  are 
the  ones  that  occur  most  frequently,  and  for  these  letters 
he  used  the  simplest  combinations  of  dots  and  dashes. 

Morse  repeatedly  said  that,  if  he  could  make  his  telegraph 
work  through  ten  miles,  he  could  make  it  work  around  the 
world.  This  promise  of  long-distance  telegraphy  he  ful- 
filled by  the  use  of  the  relay.  The  relay  works  in  the  same 
way  as  the  sounder.  The  current  coming  over  a  long  line 
may  be  too  feeble  to  produce  a  click  that  can  be  easily 
heard,  yet  strong  enough  to  magnetize  the  coils  of  the  relay 
and  cause  the  armature  to  close  another  circuit.  This 
second  circuit  includes  the  sounder  and  a  battery  in  the 
same  station  as  the  sounder,  which  we  shall  call  ''the  local 
battery."  The  relay  simply  acts  as  a  contact  key,  and  closes 
the  circuit  of  the  local  battery.  Thus  the  current  from  the 

130 


FIG.    62 MORSE'S    FIRST    TELEGRAPH    INSTRUMENT 

A  pen  was  attached  to  the  pendulum  and  drawn  across  the  strip  of 
paper  by  the  action  of  the  electromagnet.  The  lead  type  shown  in  the 
lower  right-hand  corner  was  used  in  making  electrical  contact  when  send- 
ing a  message.  The  modern  instrument  shown  in  the  lower  left-hand  cor- 
ner is  the  one  that  sent  a  message  around  the  world  in  1896. 

Photo  by  Claud  y. 


THE  STORY  OF  GREAT  INVENTIONS 


local  battery  flows  through  the  sounder  and  produces  a 
loud  click.  Sometimes  a  relay  is  used  to  control  a  second 
very  long  circuit.  At  the  farther  end  of  the  second  circuit 
may  be  a  sounder  or  a  second  relay  which  controls  a  third 
circuit.  Any  number  of  circuits  may  be  thus  connected 
by  means  of  relays.  This  is  a  form  of  repeating  system 
used  for  telegraphing  over  very  long  distances.  Fig.  63 
shows  a  circuit  with  relay  and  sounder. 

In  the  telegraphic  circuit  only  one  connecting  wire  is 


O =r 


Sounder1 


O 


Line  wire 


/?<?/, 


FIG.    63 A    TELEGRAPHIC    CIRCUIT    WITH    RELAY    AND    SOUNDER 

132 


NINETEENTH-CENTURY   INVENTIONS 


needed.  The  earth,  being  a  good  conductor  of  electricity, 
is  used  as  part  of  the  circuit.  It  is  necessary,  therefore,  to 
make  a  ground  connection  at  each  end  of  the  line,  the  in- 
struments being  connected  between  the  line  wire  and  the 


Sounder 


Sounder 


^^  Battery 


FIG.    64 A    SIMPLE    TELEGRAPHIC    CIRCUIT 

Two  keys  are  shown  at  K  K,  and  two  switches  at  5  S.  When  one  key 
is  to  be  used  the  switch  at  that  station  must  be  open,  and  the  switch 
at  the  other  station  closed. 

earth.  For  long-distance  telegraphy  a  current  from  a 
dynamo  is  used  instead  of  a  battery  current.  Fig.  64  shows 
a  simple  telegraphic  circuit. 

A  telegraphic  message  travels  with  the  speed  of  light, 
for  the  speed  of  electricity  and  the  speed  of  light  are  the 
same.  A  telegraphic  signal  would  go  more  than  seven 
times  around  the  earth  in  one  second  if  it  travelled  on  one 
continuous  wire.  The  relays  that  must  be  used,  however, 
cause  some  delay. 

'33 


THE  STORY  OF  GREAT  INVENTIONS 

In  1835  Morse's  experimental  telegraph  was  completed, 
and  in  1837  &  was  exhibited  to  the  public,  but  seven  years 
more  passed  before  a  line  was  established  for  public  use. 
Aid  from  Congress  was  necessary.  Going  to  Washington, 
Morse  exhibited  his  instrument  in  the  halls  of  the  Capitol, 
sending  messages  through  ten  miles  of  wire  wound  on  a 
reel.  The  invention  was  ridiculed,  but  the  inventor  did  not 
despair.  A  bill  for  an  appropriation  to  establish  a  tele- 
graphic line  between  Washington  and  Baltimore  passed  the 
House  by  a  small  majority.  The  last  day  of  the  session 
came.  Ten  o'clock  at  night,  two  hours  before  adjourn- 
ment, and  the  Senate  had  not  acted.  A  senator  advised 
Morse  to  go  home  and  think  no  more  of  it,  saying  that  the 
Senate  was  not  in  sympathy  with  his  project.  He  went 
to  his  hotel,  counted  his  money,  and  found  that  he  could 
pay  his  bill,  buy  his  ticket  home,  and  have  thirty-seven 
cents  left.  All  through  his  work  he  had  firmly  believed 
that  a  Higher  Power  was  directing  his  work,  and  bringing 
to  the  world,  through  his  invention,  a  new  and  uplift- 
ing force ;  and  so  when  all  seemed  lost  he  did  not  lose 
heart. 

In  the  morning  a  friend,  Miss  Ellsworth,  called  and  of- 
fered her  congratulations  that  the  bill  had  been  passed  by 
the  Senate  and  thirty  thousand  dollars  appropriated  for 
the  telegraph.  Being  the  first  to  bring  the  news  of  his 
success,  Mr.  Morse  promised  her  that  the  first  message  over 
the  new  line  should  be  hers.  In  about  a  year  the  line  was 
completed,  and  Miss  Ellsworth  dictated  the  now  famous 
message :  ' '  What  hath  God  wrought !" 

Soon  afterward  the  Democratic  Convention,  in  session  in 

134 


NINETEENTH-CENTURY   INVENTIONS 

Baltimore,  received  a  telegraphic  message  from  Senator 
Silas  Wright,  in  Washington,  declining  the  nomination  for 
the  Vice-Presidency,  which  had  been  tendered  him.  The 
convention  refused  to  accept  a  message  sent  by  telegraph, 
and  sent  a  committee  to  Washington  to  investigate.  The 
message  was  confirmed,  and  Morse  and  his  telegraph  be- 
came famous.  Fig.  65  shows  the  first  telegraph  instrument 
used  for  commercial  work. 

The  desire  to  telegraph  across  the  ocean  came  with  the 


FIG.    65 FIRST   TELEGRAPH    INSTRUMENT    USED    FOR    COMMERCIAL    WORK 

Photo  by  Claudy. 

introduction  of  the  telegraph  on  land.  Bare  wires  in  the 
air  with  glass  insulators  at  the  poles  are  used  for  land  teleg- 
raphy, but  bare  wires  in  the  water  could  not  be  used,  for 
ocean  water  will  conduct  electricity.  Something  was  needed 
to  cover  the  wire,  protect  it  from  the  water,  and  prevent 
the  escape  of  the  electric  current.  Just  when  it  was  needed 


THE  STORY  OF  GREAT  INVENTIONS 

such  a  substance  was  discovered.  In  1843,  when  Morse  was 
working  on  his  telegraph,  it  was  found  that  the  juice  of  a  cer- 
tain kind  of  tree  growing  in  the  Malayan  Archipelago  formed 
a  substance  somewhat  like  rubber  but  more  durable,  and 
especially  suited  to  the  insulation  of  wires  in  water.  This 
substance  is  gutta-percha.  Ocean  cables  are  made  of  a 
number  of  copper  wires,  each  wire  covered  with  gutta- 
percha,  the  wires  twisted  together  and  protected  with  tarred 
rope  yarn  and  an  outer  layer  of  galvanized  iron  wires.  The 
earth  is  used  for  the  return  circuit,  as  in  the  land  telegraph. 

Duplex  Telegraphy 

The  telegraph  was  a  success,  but  many  improvements 
were  yet  to  be  made.  Economy  of  construction  was  the 
thing  sought  for.  To  make  one  wire  do  the  work  of  two 
was  accomplished  by  the  invention  of  the  duplex  system. 
In  duplex  telegraphy  two  messages  may  be  sent  in  opposite 
directions  over  the  same  wire  at  the  same  time.  Let  us 
take  a  look  at  some  of  the  methods  by  which  this  is  accom- 
plished. 

One  method  with  a  long  name  but  very  simple  in  its 
working  is  the  differential  system  (Fig.  66).  In  the  differ- 
ential system  the  current  from  the  home  battery  divides 
into  two  branches  passing  around  the  coils  of  the  electro- 
magnet in  opposite  directions.  Now  if  these  two  branches 
are  so  arranged  that  the  currents  flowing  through  them  are 
equal,  the  relay  will  not  be  magnetized,  because  one  cur- 
rent would  tend  to  make  the  end  A  a  north  pole,  and  the 
pther  current  would  tend  to  make  the  same  end  a  south 

136 


THE  STORY  OF  GREAT  INVENTIONS 

pole.  The  result  is  that  the  relay  coil  is  not  magnetized, 
and  does  not  attract  the  armature.  But  the  current  from 
the  distant  battery  comes  over  one  of  these  branches  only, 
and  will  magnetize  the  relay.  Hence,  with  a  similar  ar- 
rangement at  the  second  station,  two  messages  may  be 
sent  at  the  same  time  in  opposite  directions. 

Another  method  not  quite  so  simple  in  principle  is  the 
bridge  method.  When  the  key  at  station  A  (see  Fig.  67) 
is  closed,  the  current  from  the  battery  at  station  A  divides 
at  C,  and  if  the  resistances  i  and  2  are  equal,  and  the  re- 
sistance 3  is  equal  to  the  resistance  of  the  line,  no  current 
will  flow  through  the  sounder.  But  if  a  current  comes  over 
the  line  from  the  distant  station  this  current  divides  at  D, 
and  a  part  goes  through  the  sounder,  causing  it  to  click. 
The  sounder  is  not  affected,  therefore,  by  the  current  from 
the  home  battery,  but  is  affected  by  the  current  from  the 
distant  battery.  Therefore,  a  message  may  be  sent  and 
another  received  at  the  same  time.  If  there  is  a  similar 
arrangement  at  the  other  station,  two  messages  may  travel 
over  the  line  in  opposite  directions  at  the  same  time. 

The  differential  method  is  used  in  land  telegraphy,  the 
bridge  method  almost  exclusively  in  submarine  telegraphy. 
The  next  step  was  a  quadruplex  system,  by  means  of  which 
four  messages  may  be  transmitted  over  one  wire  at  the 
same  time.  The  first  quadruplex  system  was  invented  by 
Edison  in  1874,  and  in  four  years  it  saved  more  than  half 
a  million  dollars.  Other  systems  have  been  invented  which 
make  it  possible  to  send  even  a  larger  number  of  messages 
at  one  time  over  a  single  wire. 


i 


THE  STORY  OF  GREAT  INVENTIONS 

The  Telephone 

The  idea  of  "talking  by  telegraph"  began  to  grow  in  the 
minds  of  inventors  soon  after  the  Morse  instrument  came 
into  use.  The  sound  of  the  voice  causes  vibrations  in  the 
air.  This  is  simply  shown  in  the  string  telephone.  This 
telephone  is  made  by  stretching  a  thin  membrane,  such  as 
thin  sheepskin,  or  gold-beaters'  skin,  over  a  round  frame 
of  wood  or  metal.  ,  Two  such  instruments  are  connected  by 
a  string,  the  end  of  the  string  being  fastened  to  the  middle 
of  the  stretched  membrane.  The  sound  of  the  voice  causes 
this  membrane  to  vibrate.  As  the  membrane  moves  rapid- 
ly back  and  forth,  it  pulls  and  releases  the  string,  and  so 
causes  the  membrane  at  the  other  end  to  vibrate  and  give 
out  the  sound.  This  is  the  actual  carrying  of  the  sound 
vibrations  along  the  string.  In  the  telephone  it  is  not 
sound  vibrations  but  an  electric  current  that  travels  over 
the  line  wire.  The  telephone  message,  therefore,  travels 
with  the  speed  of  electricity,  not  with  the  speed  of  sound. 
If  it  travelled  with  the  speed  of  sound  in  air,  a  message 
spoken  in  Chicago  would  be  heard  in  New  York  one  hour 
later;  but  we  know  that  a  message  spoken  in  Chicago  may 
be  heard  in  New  York  the  instant  it  is  spoken. 

The  telephone,  like  the  telegraph,  depends  on  the  electro- 
magnet. The  thought  of  inventors  at  first  was  to  make 
the  vibrations  of  a  thin  membrane,  caused  by  the  sound  of 
the  voice,  open  and  close  a  telegraphic  circuit.  An  electro- 
magnet at  the  other  end  of  the  line  would  cause  a  thin 
membrane  with  a  piece  of  soft  iron  attached  to  it  to  vibrate, 
just  as  the  magnet  in  the  telegraph  receiver  pulls  and  re- 

149 


NINETEENTH-CENTURY   INVENTIONS 

leases  the  soft-iron  armature  as  the  circuit  is  made  and 
broken.  The  thin  membrane  caused  to  vibrate  in  this  way 
would  give  out  the  sound.  A  telephone  on  this  principle 
was  invented  by  Philip  Reis,  a  schoolmaster  in  Germany, 
The  transmitter  was  carved  out  of  wood  in  the  shape  of  a 
human  ear,  the  thin  membrane  being  in  the  position  of  the 
ear-drum.  Musical  sounds  and  even  words  were  trans- 
mitted by  this  telephone,  but  it  could  never  have  been 
successful  as  a  practical  working  telephone.  The  mem- 
brane in  the  receiver  would  vibrate  with  the  same  speed 
as  the  membrane  in  the  transmitter,  but  sound  depends 
on  something  more  than  speed  of  vibration. 

The  Bell  telephone,  as  known  to-day,  began  with  a  study 
of  the  human  ear.  Alexander  Graham  Bell  was  a  teacher 
of  the  deaf.  His  aim  was  to  teach  the  deaf  to  use  spoken 
language,  and  for  this  purpose  he  wished  to  learn  the  nature 
of  the  vibrations  caused  by  the  voice.  His  plan  was  to 
cause  the  ear  itself  to  trace  on  smoked  glass  the  waves  pro- 
duced by  the  different  letters  of  the  alphabet,  and  to  use 
these  tracings  in  teaching  the  deaf.  Accordingly,  a  human 
ear  was  mounted  on  a  suitable  support,  the  stirrup-bone 
removed,  leaving  two  bones  attached,  and  a  stylus  of  wheat 
straw  attached  to  one  of  the  bones.  The  ear-drum,  caused 
to  vibrate  by  the  sound,  moved  the  two  small  bones  and 
the  pointer  of  straw,  so  that  when  he  sang  or  talked  to  the 
ear  delicate  tracings  were  made  on  the  glass. 

This  experiment  suggested  to  Mr.  Bell  that  a  membrane 
heavier  than  the  ear-drum  would  move  a  heavier  weight. 
If  the  ear-drum,  no  thicker  than  tissue-paper,  could  move 
the  bones  of  the  ear,  a  heavier  membrane  might  vibrate 

141 


THE  STORY  OF  GREAT  INVENTIONS 

a  piece  of  iron  in  front  of  an  electromagnet.  He  was  at  the 
same  time  devising  a  telegraph  for  transmitting  messages 
by  means  of  musical  sounds.  In  this  telegraph  he  was 
using  an  electromagnet  in  the  transmitter  and  another 
electromagnet  in  the  receiver.  He  attached  the  soft-iron 
armature  of  each  electromagnet  to  a  stretched  membrane 
of  gold-beaters'  skin,  expecting  that  the  sound  of  his  voice 
would  cause  the  membrane  of  the  transmitter  to  vibrate, 
and  that,  by  means  of  the  electromagnets,  the  membrane 
of  the  receiver  would  be  made  to  vibrate  in  the  same  way 
(Fig.  68).  At  first  he  was  disappointed,  but  after  making 


FIG.    68 FIRST    BELL    TELEPHONE    RECEIVER    AND    TRANSMITTER 

The  receiver  is  on  the  left  in  the  picture.  A  thin  membrane  of  gold- 
beaters' skin  tightly  stretched  and  fastened  with  a  cord  can  be  seen  on 
the  end  of  the  transmitter  and  of  the  receiver.  An  electromagnet  is  also 
shown  over  each  membrane.  This  thin  membrane,  with  a  piece  of  soft  iron 
attached,  was  used  in  place  of  the  soft-iron  disk  of  the  modern  receiver. 

142 


NINETEENTH-CENTURY   INVENTIONS 


some  changes  in  the  armatures  a  distinct  sound  was  heard 
in  the  receiver.  Later  the  membrane  was  discarded,  and 
a  thin  iron  disk  used  with  better  effect. 

The  story  of  Bell's  struggles  might  seem  like  the  repetition 
of  the  life  story  of  many  another  great  inventor.     He  knew 


FIG.    69 A    TELEPHONE    RECEIVER 

that  he  had  discovered  something  of  great  value  to  the 
world.  He  devoted  his  time  to  the  perfecting  of  the  tele- 
phone, neglecting  his  professional  work  and  finally  giving 
it  up,  that  he  might  give  his  whole  time  to  his  invention. 
He  was  forced  to  endure  poverty  and  ridicule.  He  was 
called  "a  crank  who  says  he  can  talk  through  a  wire." 
Men  said  his  invention  could  never  be  made  practical. 
Even  after  he  succeeded  in  finding  a  few  purchasers  and 
some  of  the  telephones  were  in  actual  use,  people  were  slow 
to  adopt  it.  The  idea  of  talking  at  a  piece  of  iron  and  hear- 
ing another  piece  of  iron  talk  seemed  like  a  kind  of  witchcraft. 
In  the  telephone  we  see  another  use  of  the  electromagnet. 
A  very  thin  iron  disk  near  the  poles  of  an  electromagnet 
forms  the  telephone  receiver  (Fig.  69).  An  electric  current 
travels  over  the  telephone  wire.  If  the  current  grows 
10  143 


THE  STORY  OF  GREAT  INVENTIONS 

stronger,  the  magnet  is  made  stronger  and  pulls  the  disk 
toward  it.  If  the  current  grows  weaker,  the  magnet  be- 
comes weaker  and  does  not  pull  so  hard  on  the  disk.  The 
disk  then  springs  back  from  the  magnet.  If  these  changes 
take  place  rapidly  the  disk  moves  back  and  forth  rapidly 
and  gives  out  a  sound.  The  sound  of  the  voice  at  the 
other  end  of  the  line  sets  the  disk  in  the  mouthpiece  vibrat- 
ing. The  vibrations  of  this  disk  cause  the  changes  in  the 
electric  current  flowing  over  the  line-wire,  and  the  changes 
in  the  electric  current  cause  the  disk  of  the  receiver  to  vi- 
brate in  exactly  the  same  way  as  the  disk  at  the  mouth- 
piece. Thus  the  words  spoken  into  the  mouthpiece  may 
be  heard  at  the  receiver. 

The  transmitter  used  by  Bell  was  like  the  receiver.  Two 
receivers  from  the  common  telephone  connected  by  two 
wires  may  be  used  as  a  telephone  without  batteries.  Fig.  70 
shows  a  complete  telephone  made  of  two  receivers  con- 
nected by  two  wires.  The  disk  in  one  receiver  which  is  now 
used  as  a  transmitter  is  made  to  vibrate  by  the  sound  of  the 
voice.  Now  when  a  piece  of  iron  moves  back  and  forth  in 
a  magnetic  field  it  strengthens  and  weakens  the  field.  So 
the  magnetic  field  in  the  transmitter  is  rapidly  changed  by 
the  movement  of  the  iron  disk.  Now  we  have  found  that 
whenever  a  coil  of  wire  is  in  a  changing  magnetic  field  a 
current  is  induced  in  the  coil.  The  small  coil  in  the  trans- 
mitter, therefore,  has  a  current  induced  in  it.  We  have  also 
found  that  when  the  magnetic  field  is  made  stronger  the 
induced  current  flows  in  one  direction,  and  when  the  field 
is  made  weaker  the  current  flows  in  the  opposite  direction. 
Since  the  field  in  the  transmitter  is  made  alternately  stronger 

144 


NINETEENTH-CENTURY   INVENTIONS 


and  weaker,  the  current  in  the  coil  flows  first  in  one  direc- 
tion,- then  in  the  opposite  direction  —  that  is,  we  have  an 
alternating  current.  This  alternating  current,  of  course, 


y^.*aa£ 
fc/«  _Tf 


-«*    t*. 


FIG.    70 TWO    RECEIVERS    USED    AS    A    COMPLETE    TELEPHONE 

flows  over  the  line-wire  and  through  the  coil  in  the  receiver. 
In  the  receiver  the  alternating  current  will  alternately 
strengthen  and  weaken  the  magnetic  field,  and  as  it  does  so 
the  pull  of  the  magnet  on  the  iron  disk  is  strengthened  and 
weakened.  The  iron  disk  in  the  receiver,  therefore,  vi- 
brates in  exactly  the  same  way  as  the  disk  in  the  transmit- 
ter, and  so  gives  out  a  sound  just  like  that  which  is  acting 
on  the  transmitter. 


THE  STORY  OF  GREAT  INVENTIONS 


In  the  Blake  transmitter,  which  is  now  commonly  used, 
the  disk  moves  a  pencil  of  carbon  which  presses  against 
another  pencil  of  carbon.  This  varies  the  pressure  between 
the  two  pencils  of  carbon.  A  battery  current  flows  through 
the  two  carbons,  and  as  the  pressure  of  the  carbons  changes 
the  strength  of  the  current  changes.  When  the  carbons  are 
pressed  together  more  closely  the  current  is  stronger.  When 
the  pressure  is  less  the  current  is  weaker.  We  have,  then, 
a  varying  current  through  the  carbons.  This  current  flows 

through  the  primary  coil  of  an 
induction-coil,  the  secondary 
being  connected  to  the  line- 
wire.  Now  a  current  of  vary- 
ing strength  in  the  primary 
induces  an  alternating  current 
in  the  secondary.  We  have, 
DIAPHRAGM  then,  an  alternating  current 
flowing  over  the  line -wire. 
This  alternating  current  acts 
on  the  magnetic  field  of  the 
receiver  in  the  way  described 
before,  causing  the  disk  in  the 
receiver  to  vibrate  and  give 
out  the  sound. 

For  long-distance  work  a 
carbon -dust  transmitter  (Fig. 
71)  is  used.  In  this  there  are 
many  granules  of  carbon,  so 
that  instead  of  two  carbon-points  in  contact  there  are  many. 
This  makes  the  transmitter  more  sensitive. 

146 


CARBON 
DUST 


FIG.    71 CARBON-DUST    TRANS- 
MITTER 


NINETEENTH-CENTURY    INVENTIONS 

The  strength  of  current  required  for  the  telephone  is  very 
small.  To  transmit  a  telephone  message  requires  less  than 
a  hundred -millionth  part  of  the  current  required  for  a  tele- 
graphic message.  The  work  done  in  lifting  the  telephone 
receiver  a  distance  of  one  foot,  if  changed  into  an  alternating 
current,  would  be  sufficient  to  keep  up  a  sound  in  the  re- 
ceiver for  a  hundred  thousand  years.  Because  of  its  extreme 
sensitiveness  the  telephone  requires  a  complete  wire  circuit. 
The  earth  cannot  be  used  for  the  return  circuit,  as  in  the 
case  of  the  telegraph.  Disturbances  in  the  earth,  vibra- 
tion, leakage  currents  from  trolley  lines,  and  so  forth,  would 
interfere  seriously  with  the  action  of  the  telephone. 

When  the  telephone  was  invented  it  was  commonly  re- 
marked that  it  could  not  take  the  place  of  the  telegraph 
in  commerce,  for  the  latter  gave  the  merchant  some  evidence 
of  a  business  transaction,  while  the  telephone  left  no  sign. 
There  was  a  time  when  men  feared  to  trust  each  other,  but 
now  large  business  deals  are  made  by  telephone;  products 
of  the  farm,  the  factory,  and  the  mine  are  bought  and  sold 
in  immense  quantities  without  a  written  contract  or  even 
the  written  evidence  of  a  telegram.  Thus  the  telephone  has 
developed  a  spirit  of  business  honor. 

The  Phonograph 

The  phonograph  grew  out  of  the  telephone.  It  is  said 
to  be  the  only  one  of  Edison's  inventions  that  came  by 
accident,  yet  only  a  man  of  genius  would  have  seen  the 
meaning  of  such  an  accident.  He  was  singing  into  the 
mouthpiece  of  a  telephone  when  the  vibrations  of  the  disk 


THE  STORY  OF  GREAT  INVENTIONS 

caused  a  fine  steel  point  to  pierce  one  of  his  fingers  held  just 
behind  the  disk.  This  set  him  to  thinking.  If  the  sound 
of  his  voice  could  cause  the  disk  to  vibrate  with  force 
enough  to  pierce  the  skin,  would  it  not  make  impressions 
on  tin-foil,  and  so  make  a  record  of  the  voice  that  could 
be  reproduced  by  passing  the  point  rapidly  over  the  same 
impressions?  He  gave  his  assistants  the  necessary  in- 
structions, and  soon  the  first  phonograph  was  made. 

This  disk  in  the  phonograph  is  set  in  vibration  by  sound 
vibrations  in  the  air  in  the  same  way  as  the  disk  in  the  tele- 
phone transmitter.  Attached  to  the  disk  is  a  needle-point 
which,  of  course,  vibrates  with  the  disk.  If  a  cylinder  with 
a  soft  surface  is  turned  rapidly  under  the  steel  point  as  it- 
vibrates,  impressions  are  made  in  the  cylinder  correspond- 
ing to  the  movements  of  the  disk.  The  cylinder  must  move 
forward  as  it  turns,  so  that  its  path  will  be  a  spiral.  If,  now, 
the  stylus  is  placed  at  the  starting-point  and  the  cylinder 
turned  rapidly  the  stylus  will  move  rapidly  up  and  down 
as  it  goes  over  the  indentations  in  the  cylinder,  and  so  cause 
the  metal  disk  to  vibrate  and  give  out  a  sound  like  that 
received  at  first.  In  the  earliest  phonographs  the  cylinder 
was  covered  with  tin-foil.  Later  the  so-called  "wax  rec- 
ords" came  into  use.  These  cylinders  are  not  made  of  wax, 
but  of  very  hard  soap.  Fig. v  72  shows  an  instrument  in 
which  the  sound  of  the  voice  caused  a  pencil-point  to  trace 
a  wavy  line  on  a  cylinder.  This  instrument  may  be  called 
a  forerunner  of  the  phonograph.  Fig.  73  shows  Edison's 
first  phonograph  with  a  modern  instrument  placed  beside 
it  for  comparison. 


THE  STORY  OF  GREAT  INVENTIONS 

Gas-Engines 

Cannons  are  the  oldest  gas-engines.  Indeed,  the  prin- 
ciple of  the  cannon  is  the  same  as  that  of  the  modern  gas- 
engine,  the  piston  in  the  engine  taking  the  place  of  the 
cannon-ball.  The  power  in  each  case  is  obtained  by  ex- 
plosion —  in  the  cannon  the  explosion  of  powder,  in  the 
engine  the  explosion  of  a  mixture  of  air  and  gas.  Powder- 
engines  with  pistons  were  proposed  in  the  seventeenth  cen- 


FIG.   73 EDISON  S    FIRST    PHONOGRAPH    AND    A    MODERN    INSTRUMENT 

Photo  by  Claudy. 

.tury,  and  some  were  actually  built,  but  it  proved  too  diffi- 
cult to  control  them,  and  the  idea  of  the  gas-engine  was 
abandoned  for  more  than  a  hundred  years. 

The  discovery  of  coal-gas  near  the  close  of  the  eighteenth 
century  gave  a  new  impetus  to  the  gas-engine.  John  Bar- 
ber, an  Englishman,  built  the  first  actual  gas-engine.  He 

150 


NINETEENTH-CENTURY   INVENTIONS 

used  gas  distilled  from  wood,  coal,  or  oil.  The  gas,  mixed 
with  the  proper  proportion  of  air,  was  introduced  into  a  tank 
which  he  called  the  exploder.  The  mixture  was  fired  and 
issued  out  in  a  continuous  stream  of  flame  against  the 
vanes  of  a  paddle-wheel,  driving  them  round  with  great 
force. 

In  1804  Lebon,  a  French  engineer,  was  assassinated,  and 
the  progress  of  the  gas-engine  set  back  a  number  of  years, 
for  this  engineer  had  proposed  to  compress  the  mixture  of 
gas  and  air  before  firing,  and  to  fire  the  mixture  by  an 
electric  spark.  This  is  the  method  used  in  gas-engines 
to-day. 

The  first  practical  working  gas-engine  was  invented  by 
Lenoir,  a  Frenchman,  in  1860.  From  this  time  to  the  end 
of  the  century  the  gas-engine  developed  rapidly,  receiving 
a  new  impulse  from  the  increasing  demand  for  the  motor- 
car. 

The  engine  of  the  German  inventors,  Otto  and  Langen, 
brought  out  in  1876,  marked  the  beginning  of  a  new  era. 
The  greater  number  of  engines  used  in  automobiles  to-day 
are  of  the  kind  known  as  the  Otto  cycle,  or  four-cycle, 
engine.  This  engine  is  called  four-cycle  because  the  piston 
makes  four  strokes  for  every  explosion.  There  is  one  stroke 
to  admit  the  mixture  of  gas  and  air  to  the  cylinder,  another 
to  compress  the  gas  and  air,  at  the  beginning  of  the  third 
stroke  the  explosion  takes  place,  and  in  the  fourth  stroke  the 
burned-out  gases  are  driven  out  of  the  cylinder.  The  work- 
ing of  the  four-cycle  gas-engine  is  made  clear  in  Figs.  74, 
75,  76,  and  77. 

In  such  a  gas-engine  the  power  .is  applied  to  the  piston 


FIG.    74 FIRST   STROKE.       GAS   AND   AIR  ADMITTED   TO   THE   CYLINDER 


FIG.    75 SECOND    STROKE.       MIXTURE    OF    GAS    AND    AIR    COMPRESSED 


FIG.    76 THIRD    STROKE.       THE    MIXTURE    IS    EXPLODED    AND    EXPANDS, 

DRIVING    THE    PISTON    FORWARD 


FIG.    77 FOURTH    STROKE,    EXHAUST.       THE    BURNED-OUT   MIXTURE    OF 

GAS    AND    AIR   EXPELLED    FROM    THE    CYLINDER 


THE    FOUR-CYCLE    GAS-ENGINE 


NINETEENTH-CENTURY   INVENTIONS 

only  in  one  stroke  out  of  every  four,  while  in  the  steam- 
engine  the  power  is  applied  at  every  stroke.  It  would  seem, 
therefore,  that  a  steam-engine  would  do  more  work  than  a 
gas-engine  for  the  same  amount  of  heat,  but  such  is  not  the 
case;  in  fact,  a  good  gas-engine  will  do  about  twice  as 
much  work  as  a  good  steam-engine  for  the  same  amount  of 
fuel.  The  reason  is  that  the  steam-engine  wastes  its  heat. 
Heat  is  given  to  the  condenser,  to  the  iron  of  the  boiler,  to 
the  connecting  pipes  and  the  air  around  them,  while  in  the 
gas-engine  the  heat  is  produced  in  the  cylinder  by  the  ex- 
plosion and  the  power  applied  directly  to  the  piston-head. 
More  than  this,  a  steam-engine  when  at  rest  wastes  heat; 
there  must  be  a  fire  under  the  boiler  if  the  engine  is  to  be 
ready  for  use  on  short  notice.  When  a  gas-engine  is  at  rest 
there  is  no  fire,  nothing  is  being  used  up,  and  yet  the  engine 
can  be  started  very  quickly.  A  gas-engine  can  be  made 
much  lighter  than  a  steam-engine  of  the  same  horse-power. 
The  automobile  and  the  flying-machine  require  very  light 
engines.  Without  the  gas-engine  the  automobile  would  have 
remained  imperfect  and  crude,  while  the  flying-machine 
would  have  been  impossible. 

In  a  two-cycle  gas-engine  there  is  an  explosion  for  every 
two  strokes  of  the  piston,  or  one  explosion  for  every  revo- 
lution of  the  crank-shaft.  During  one  stroke  the  mixture 
of  gas  and  air  on  one  side  of  the  piston  is  compressed  and 
a  new  mixture  enters  on  the  opposite  side  of  the  piston. 
At  the  end  of  this  stroke  the  compressed  mixture  is  ex- 
ploded, and  power  is  applied  to  the  piston  during  about 
one-fourth  of  the  next  stroke.  During  the  remainder  of 
the  second  stroke  the  burned-out  gas  escapes,  and  the  fresh 


THE  STORY  OF  GREAT  INVENTIONS 

mixture  passes  over  from  one  side  of  the  piston  to  the  other 
ready  for  compression.  The  two-cycle  engine  is  simpler  in 
construction  than  the  four-cycle,  having  no  valves.  It  also 


FIG.      78 TWO-CYCLE     GAS-ENGINE.         CRANK     AND     CONNECTING-ROD     ARE 

ENCLOSED    WITH    THE    PISTON 

has  less  weight  per  horse-power.  The  cylinder  of  a  two- 
cycle  engine  is  shown  in  Fig.  78. 

A  steam-engine  is  self-starting.  The  engineer  has  only 
to  turn  the  steam  into  the  cylinder,  but  the  gas-engine  re- 
quires to  be  turned  until  at  least  one  explosion  takes  place, 
for  until  there  is  an  explosion  of  gas  and  air  in  the  cylinder 
there  is  no  power. 

A  gas-engine  may  have  a  number  of  cylinders.  Four- 
cylinder  and  six-cylinder  engines  are  common.  In  a  four- 
cylinder,  four-cycle  engine,  while  one  cylinder  is  on  the 
power  stroke  the  next  is  on  the  compression  stroke,  the 
third  on  the  admission  stroke,  and  the  fourth  on  the  exhaust 
stroke.  Fig.  79  shows  the  Selden  " explosion  buggy"  pro- 


NINETEENTH-CENTURY   INVENTIONS 

pelled  by  a  gas-engine.     This  machine  was  the  forerunner 
of  the  modern  automobile. 


The  Steam  Locomotive 

Late  in  the  eighteenth  century  a  mischievous  boy  put 
some  water  in  a  gun-barrel,  rammed  down  a  tight  wad,  and 
placed  the  barrel  in  the  fire  of  a  blacksmith's  forge.  The 
wad  was  thrown  out  with  a  loud  report,  and  the  boy's  play- 
mate, Oliver  Evans,  thought  he  had  discovered  a  new 


FIG.  79 SELDEN    "EXPLOSION    BUGGY."       FORERUNNER    OF    THE    MODERN 

AUTOMOBILE 

155 


THE  STORY  OF  GREAT  INVENTIONS 

power.  The  prank  with  the  gun-barrel  set  young  Evans 
thinking  about  the  power  of  steam.  It  was  not  long  until 
he  read  a  description  of  a  Newcomen  engine.  In  the  New- 
comen  engine,  you  will  remember,  it  was  the  pressure  of 
air,  not  the  pressure  of  steam,  that  lifted  the  weight.  Evans 
soon  set  about  building  an  engine  in  which  the  pressure  of 
steam  should  do  the  work.  He  is  sometimes  called  the 
"Watt  of  America,"  for  he  did  in  America  much  the  same 
work  that  Watt  did  in  Scotland.  Evans  built  the  first 
successful  non-condensing  engine — that  is,  an  engine  in 
which  the  steam,  after  driving  the  piston,  escapes  into  the 
air  instead  of  into  a  condenser.  The  non-condensing  en- 
gine made  the  locomotive  possible,  for  a  locomotive  could 
not  conveniently  carry  a  condenser.  Evans  made  a  loco- 
motive which  travelled  very  slowly.  He  said,  however: 
"The  time  will  come  when  people  will  travel  in  stages 
moved  by  steam-engines  from  one  city  to  another,  almost 
as  fast  as  birds  can  fly,  fifteen  or  twenty  miles  an  hour." 

The  inventor  who  made  the  first  successful  locomotive 
was  George  Stephenson,  and  it  is  worth  noting  that  one  of 
his  engines,  the  "Rocket,"  possessed  all  the  elements  of 
the  modern  locomotive.  He  combined  in  the  "Rocket" 
the  tubular  boiler,  the  forced  draft,  and  direct  connec- 
tion of  the  piston-rod  to  the  crank-pin  of  the  driving- 
wheel. 

The  " Rocket"  was  used  on  the  first  steam  railway  (the 
Stockton  &  Darlington,  in  England) ,  which  was  opened  in 
1825.  There  had  been  other  railways  for  hauling  coal  by 
means  of  horses  over  iron  tracks,  and  other  locomotives  that 
travelled  over  an  ordinary  road ;  but  this  was  the  first  road 


NINETEENTH-CENTURY   INVENTIONS 

on  which  a  steam-engine  pulled  a  load  over  an  iron  track, 
the  first  real  railroad.  Fig.  80  shows  the  " Rocket"  and 
two  other  early  locomotives. 

In  order  to  build  a  railroad  between  Liverpool  and  Man- 
chester for  carrying  both  passengers  and  freight  it  was 
necessary  to  secure  an  act  of  Parliament.  Stephenson  was 
compelled  to  undergo  a  severe  cross-examination  by  a  com- 
mittee of  Parliament,  who  feared  there  would  be  great 
danger  if  the  speed  of  the  trains  were  as  high  as  twelve 
miles  an  hour.  He  was  asked: 

"Have  you  seen  a  railroad  that  would  stand  a  speed  of 
twelve  miles  an  hour?" 

"Yes." 

"Where?" 

"Any  railroad  that  would  bear  going  four  miles  an  hour. 
I  mean  to  say  that  if  it  would  bear  the  weight  at  four  miles 
an  hour  it  would  bear  it  at  twelve." 

* '  Do  you  mean  to  say  that  it  would  not  require  a  stronger 
railway  to  carry  the  same  weight  at  twelve  miles  an  hour?" 

"I  will  give  an  answer  to  that.  I  dare  say  every  person 
has  been  over  ice  when  skating,  or  seen  persons  go  over, 
and  they  know  that  it  would  bear  them  better  at  a  greater 
velocity  than  it  would  if  they  went  slower;  when  they  go 
quickly  the  weight,  in  a  measure,  ceases." 

"Would  not  that  imply  that  the  road  must  be  perfect?" 

"It  would,  and  I  mean  to  make  it  perfect." 

For  seven  miles  the  road  must  be  built  over  a  peat  bog 
into  which  a  stone  would  sink  to  unknown  depths.  To 
convince  the  committee,  however,  and  secure  the  act  of 
Parliament  was  more  difficult  than  to  build  the  road.  But 


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NINETEENTH-CENTURY   INVENTIONS 

Stephenson  was  one  of  the  men  who  do  things  because  they 
never  give  up,  and  the  road  was  built. 


How  a  Locomotive  Works 

To  understand  how  a  locomotive  works,  let  us  consider 
how  the  steam  is -produced,  how  it  acts  on  the  piston,  and 
how  it  is  controlled.  The  steam  is  produced  in  a  locomotive 
in  exactly  the  same  way  that  steam  is  produced  in  a  tea- 
kettle. Now  everybody  knows  that  a  quart  of  water  in  a 
tea-kettle  with  a  wide  bottom  placed  on  a  stove  will  boil 
more  quickly  than  the  same  amount  of  water  in  a  tea-pot 
with  a  narrow  bottom.  The  greater  the  heating-surface— 
that  is,  the  greater  the  surface  of  heated  metal  in  contact 
with  the  water — the  more  quickly  the  water  will  boil  and 
the  more  quickly  steam  can  be  produced.  In  a  locomotive 
the  aim  is  to  use  as  large  a  heating-surface  as  possible.  This 
is  done  by  making  the  fire-box  double  and  allowing  the  water 
to  circulate  in  the  space  between  the  inner  and.  outer  parts, 
except  underneath;  also  by  placing  tubes  in  the  boiler 
through  which  the  heated  gases  and  smoke  from  the  fire 
must  pass.  An  ordinary  locomotive  contains  two  hundred 
or  more  of  these  tubes.  The  water  surrounds  these  tubes, 
and  is  therefore  in  contact  with  a  very  large  surface  of 
heated  metal.  In  some  engines  the  water  is  in  the  tubes, 
and  the  heated  gases  surround  the  tubes. 

The  steam  as  it  enters  the  cylinder  should  be  dry — that 
is,  it  should  not  contain  drops  of  water.  This  is  accom- 
plished by  allowing  the  steam  from  the  boiler  to  pass  into 
a  dome  above  the  boiler.  Here  the  steam,  which  is  nearly 


THE  STORY  OF  GREAT  INVENTIONS 

dry,  enters  a  steam-pipe  leading  to  the  cylinder  (Fig.  81). 
The  steam  is  admitted  to  the  cylinder  by  means  of  a  slide- 
valve.  From  the  diagram  it  can  easily  be  seen  that  the 
valve  admits  steam  first  on  one  side  of  the  piston,  then  on 
the  other.  It  can  also  be  seen  that  the  valve  closes  the 
admission-port,  and  so  cuts  off  the  steam  before  the  piston 
has  made  a  full  stroke.  The  steam  that  is  shut  up  in  the 
cylinder  continues  to  expand  and  act  on  the  piston.  At  the 
same  time  the  valve  opens  the  exhaust-port,  allowing  the 
steam  to  escape  from  the  other  side  of  the  piston;  but  it 
closes  this  port  before  the  piston  has  quite  finished  the 
stroke.  The  small  quantity  of  steam  thus  shut  up  acts  like 
a  cushion  to  prevent  the  piston  striking  the  end  of  the 
cylinder  with  too  great  force.  The  exhaust-steam  escapes 
through  a  blast-pipe  into  the  chimney,  drives  the  air  before 
it  up  the  chimney,  and  thus  makes  a  greater  draft  of  air 
through  the  fire-box.  This  is  called  the  forced  draft.  The 
escape  of  the  exhaust-steam  causes  the  puffing  of  the  loco- 
motive just  after  starting.  After  the  engine  is  under  way 
the  engineer  partly  shuts  off  the  steam  by  means  of  the 
reversing  lever  and  the  puffing  is  less  noticeable. 

The  action  of  the  steam  may  be  summed  up  as  follows: 

1.  Steam  admitted  to  the  cylinder  (admission). 

2.  Valve  closes  admission -port  (cut-off). 

3 .  Steam  shut  up  in  the  cylinder  expands,  acting  on  the 
piston  (expansion  period). 

4.  Valve   opens  exhaust  -  port  to  allow  used   steam  to 
escape  (exhaust). 

The  devices  for  controlling  the  steam  are  the  throttle- 
valve  and  the  valve-gear.     The  throttle-valve  is  at  the  en- 

160 


p  O 

O  oo 

3  7 

<o  I 

S-  g 


= 


s-  S 


THE  STORY  OF  GREAT  INVENTIONS 

trance  to  the  steam-pipe  in  the  steam-dome.  This  valve  is 
opened  and  closed  by  means  of  a  rod  in  the  engineer's 
cab. 

Stephenson's  link-motion  valve-gear  is  used  on  most  loco- 
motives. The  forward  rod  in  the  diagram  is  in  position  to 
act  upon  the  valve-rod  through  the  lever  L.  Suppose  the 
reversing-lever  is  drawn  back  to  the  dotted  line ;  then  the  for- 
ward rod  will  be  raised  and  the  backward  rod  will  come  into 
position  to  act  on  the  lever  L.  If  this  is  done  while  the  loco- 
motive is  at  rest  the  valve  is  moved  through  one-half  a  com- 
plete stroke.  In  the  diagram  the  steam  enters  the  cylinder 
on  the  right  of  the  piston.  After  this  movement  of  the  valve 
the  steam  would  enter  on  the  left  side  of  the  piston.  In  the 
present  position  the  locomotive  would  move  forward,  but 
if  the  valve  is  changed  so  as  to  admit  steam  to  the  left  of 
the  piston  while  the  connecting-rod  is  in  the  position  shown 
then  the  engine  will  move  backward.  Thus  the  direction 
can  be  controlled  by  the  engineer  in  the  cab.  Of  course, 
this  can  be  done  while  the  engine  is  in  motion.  The  for- 
ward rod  and  the  backward  rod  are  each  moved  by  an 
eccentric  on  the  axle  of  the  front  driving-wheel.  The  two 
eccentrics  are  in  opposite  positions  on  the  axle.  An  eccen- 
tric acts  just  like  a  crank,  causing  the  rod  to  move  forward 
and  backward  as  the  axle  turns,  and  of  course  this  motion 
is  given  to  the  valve-rod  through  the  lever.  When  the  link 
is  set  midway  between  the  forward  and  the  backward  rod 
the  valve  cannot  move.  When  the  link  is  raised  or  lowered 
part  way  the  valve  makes  a  short  stroke,  and  less  steam  is 
admitted  to  the  cylinder  than  with  a  full  stroke.  In  start- 
ing the  locomotive  the  valve  is  set  to  make  a  full  stroke. 

162 


NINETEENTH-CENTURY   INVENTIONS 

When  the  train  is  under  headway  the  valve  is  set  for  a  short 
stroke  to  economize  steam.  The  valve-gear  and  the  throttle- 
valve  together  take  the  place  of  the  governor  in  the  station- 
ary engine,  but  while  the  governor  acts  automatically  these 
are  controlled  by  the  engineer. 

In  reality  a  locomotive  is  two  engines,  one  on  either  side, 
connected  to  the  same  driving-wheels.  But  the  two  piston- 
rods  are  connected  to  the  driving-wheels  at  points  which 
are  at  right  angles  with  each  other,  so  that  when  the  crank 
on  one  side  is  at  the  end  of  a  stroke — the  "dead  centre" — 
that  on  the  other  side  is  on  the  quarter,  either  above  or 
below  the  axle,  ready  for  applying  the  greatest  turning 
force. 

The  expansion-engine  was  designed  to  use  more  of  the 
power  of  the  steam  than  can  be  done  in  the  single-cylinder 
engine.  In  the  double  expansion-engine  the  steam  expands 
from  one  cylinder  into  another.  The  second  cylinder  must 
be  larger  in  diameter  than  the  first.  In  the  triple  expansion- 
engine  the  steam  expands  from  the  second  cylinder  into  a 
third,  still  larger.  The  second  and  third  cylinders  use  a 
large  part  of  the  power  that  would  be  wasted  with  only  one 
cylinder. 

The  Turbine 

One  of  the  great  inventions  relating  to  steam-power  is 
the  steam-turbine.  The  water-turbine  is  equally  useful  in 
relation  to  water-power.  The  water-turbine  and  the  steam- 
turbine  work  in  very  much  the  same  way,  the  difference 
being  due  to  the  fact  that  steam  expands  as  it  drives  the 
engine,  while  water  drives  it  by  its  weight  in  falling,  or  by 


THE  STORY  OF  GREAT  INVENTIONS 


its  motion  as  it  rushes  in  a  swift  stream  or  jet  against  the 
blades  of  the  turbine. 

The  first  steam-engine,  that  of  Hero  in  the  time  of  Archi- 
medes, was  a  form  of  turbine  (Fig.  82).     It  was  driven  by 

the  reaction  of  the  steam  as 
it  escaped  into  the  air.  The 
common  lawn-sprinkler,  that 
whirls  as  the  water  rushes 
through  it,  is  a  water  -  turbine 
that  works  in  the  same  way. 
"Barker's  Mill"  is  the  name 
applied  to  a  water-turbine  that 
works  like  the  lawn-sprinkler. 
As  the  water  rushes  out  of  the 
opening  it  pushes  against  the 
air.  It  cannot  push  against 
the  air  without  pushing  back 
at  the  same  time.  Never  yet 
has  any  person  or  object  in 
nature  been  able  to  push  in 
one  direction  only.  It  can- 
not be  done.  If  you  push 

a  cart  forward  you  push  backward  against  the  ground 
at  the  same  time.  If  there  were  nothing  for  you  to  push 
back  against  your  forward  push  would  not  move  the  cart 
a  hair's-breadth.  If  you  doubt  this,  try  to  push  a  cart 
when  you  are  standing  on  ice  so  slippery  that  you  cannot 
get  a  foothold.  It  is  the  backward  push  of  the  water  in  the 
lawn-sprinkler  and  the  backward  push  of  the  steam  in 
Hero's  engine  that  cause  the  machine  to  turn. 

164 


FIG.    82 HERO'S    ENGINE 


NINETEENTH-CENTURY   INVENTIONS 

The  turbines  in  common  use  for  both  water  and  steam 
power  have  curved  blades.  The  reason  for  curving  the 
blades  can  best  be  seen  by  referring  to  an  early  form  of 
water-wheel.  The  best  water-turbine  is  only  an  improved 
form  of  water-wheel.  The  first  water-wheels  had  flat 
blades,  and  these  answered  very  well  so  long  as  only  a  low 
power  was  needed  and  it  was  not  necessary  to  save  the 
power  of  the  water.  It  was  found,  however,  that  there 
was  a  great  waste  of  power  in  the  wheel  with  flat  blades. 
One  inventor  proposed  to  improve  the  wheel  by  curving  the 


PIG.    83 AN    UNDERSHOT    WATER-WHEEL   WITH    CURVED    BLADES 

blades  in  such  a  way  that  the  water  would  glide  up  the 
curve  and  then  drop  directly  downward  (Fig.  83).  The 
water  then  gives  up  practically  all  of  its  power  to  the  wheel 
and  falls  from  the  wheel.  It  would  have  no  power  to 

165 


THE  STORY  OF  GREAT  INVENTIONS 

move  a  second  wheel.  In  this  way  he  used  practically 
all  the  power  of  the  water.  To  save  the  power  of  the  water 
by  making  all  of  the  water  strike  the  wheel  at  high  speed 


FIG.    84 AN    OVERSHOT    WATER-WHEEL 


the  channel  was  made  narrow  just  above  the  wheel,  form- 
ing a  mill-race.  This  applies  to  the  undershot  wheel.  In 
the  overshot  wheel  (Fig.  84)  the  power  depends  on  the 
weight  of  the  water  and  on  its  height.  The  water  runs  into 
buckets  attached  to  the  wheel,  and,  as  it  falls  in  these 
buckets,  turns  the  wheel.  The  undershot  wheel  and  the 

166 


NINETEENTH-CENTURY   INVENTIONS 


some 


mill-race  represent  a  common  form  of  turbine,  that  form  in 
which  the  steam  or  the  water  is  forced  in  a  jet  against  a 
set  of  curved  blades.  Fig.  85  shows  a  steam-turbine  run 
by  a  jet  of  steam.  In  the  water-turbine  there  are  two  sets 
of  blades.  One  set  rotates,  the  other  remains  fixed.  The 
use  of  the  fixed  blades  is  to  turn  the  water  and  drive  it  in 
the  right  direction  against  the  moving  blades.  In 
forms  of  turbine  there  are 
more  than  two  sets  of 
blades.  The  steam,  as  it 
passes  through,  gives  up 
some  of  its  power  to  each 
set  of  blades  until,  after 
passing  the  last  set,  it  has 
given  up  nearly  all  its  pow- 
er. The  action  of  the  steam 
in  this  turbine  is  somewhat 
like  that  in  the  expansion- 
engine,  in  which  the  steam 
gives  up  a  portion  of  its 
power  in  each  cylinder. 
Fig.  86  is  from  a  photo- 
graph of  a  modern  steam- 
turbine,  and  Fig.  87  is  a 
drawing  of  the  same  tur- 
bine showing  the  course  of  the  steam, 
that  runs  a  large  dynamo. 

In  1897,  as  the  battle-ships  of  the  British  fleet  were  as- 
sembled to  celebrate  the  Diamond  Jubilee  of  Queen  Victoria, 
a  little  vessel  a  hundred  feet  long  darted  in  and  out  among 

167 


FIG.  85 DE    LAVAL   STEAM-TURBINE 

Driven  by  a  jet  of  steam  striking 
the  blades.  . 


Fig.  88  is  a  turbine 


p  I 

3    ° 

2  > 
^    o 

M 

3  o 


THE  STORY  OF  GREAT  INVENTIONS 

the  giant  ships,  defied  the  patrol-boats  whose  duty  it  was 
to  keep  out  intruders,  and  raced  down  the  lines  of  battle- 
ships at  the  then  unheard-of  speed  of  thirty-five  knots  an 
hour.  It  was  the  Turbinia,  fitted  with  the  Parsons  turbine. 
This  event  marked  the  beginning  of  the  modern  turbine. 


FIG.    88 A    STEAM-TURBINE     THAT     RUNS    A    DYNAMO     GENERATING     I4,OOO 

ELECTRICAL    HORSE-POWER 

The  steam  enters  through  the  large  pipe  at  the  left. 

It  also  marked  the  beginning  of  a   revolution   in   steam 
propulsion. 

The  Parsons  turbine  does  not  use  the  jet  method,  but 
the  steam  enters  near  the  centre  of  the  wheel  and  flows 

170 


NINETEENTH-CENTURY   INVENTIONS 

toward  the  rim,  passing  over  a  number  of  rows  of  curved 
blades.  The  Parsons  turbine  is  used  on  the  fastest  ocean 
liners.  The  Lusitania,  one  of  the  fastest  steamships  in  the 
first  decade  of  the  twentieth  century,  has  two  sets  of  high 
and  low  pressure  turbines  with  a  total  of  68,000  horse-power. 

The  windmill  is  a  form  of  turbine  driven  by  the  air.  As 
the  air  rushes  against  the  blades  of  the  windmill,  it  forces 
them  to  turn.  If  the  windmill  were  turned  by  some  me- 
chanical power,  it  would  drive  the  air  back,  and  we  should 
have  a  blower.  This  is  what  we  have  in  the  electric  fan, 
a  small  windmill  driven  by  an  electric  motor  so  that  it 
drives  the  air  instead  of  being  driven  by  it.  The  blades  of 
the  windmill  and  the  electric  fan  are  shaped  very  much 
like  the  screw  propeller.  The  screw  propeller,  driven  by 
an  engine,  would  drive  the  water  back  if  the  ship  were 
firmly  anchored,  just  as  the  fan  drives  the  air.  But  it  can- 
not drive  the  water  back  without  pushing  forward  on  the 
ship  at  the  same  time,  and  this  forward  push  propels  the 
ship.  It  is  difficult  to  attain  what  is  now  regarded  as  high 
speed  with  a  single  screw.  With  engines  in  pairs  and  two 
lines  of  shafting  higher  power  can  be  used.  The  best 
steamers,  therefore,  are  fitted  with  the  twin-screw  pro- 
peller. Some  large  steamers  have  three  and  some  four 
screws. 

The  screw  propellers  of  turbine  steamships  are  made  of 
small  diameter,  that  they  may  rotate  at  high  speed  without 
undue  waste  of  power.  By  the  use  of  turbine  engines  and 
twin-screw  propellers,  the  weight  of  the  machinery  has  been 
greatly  reduced.  The  old  paddle-wheels,  with  low-pressure 
engines,  developed  only  about  two  horse-power  for  each 

171 


THE  STORY  OF  GREAT  INVENTIONS 

ton  of  machinery.  The  turbine,  with  the  twin-screw  pro- 
peller, develops  from  six  to  seven  horse-power  for  every 
ton  of  machinery.  The  modern  steamer,  with  all  its  ma- 
chinery and  coal  for  an  Atlantic  voyage,  weighs  no  more 
than  the  engines  of  the  old  paddle-wheel  type  and  coal 
would  weigh  for  the  same  horse-power.  The  steam-turbine 
and  the  twin-screw  propeller  have  made  rapid  ocean  travel 
possible. 


Chapter  VI 

THE  TWENTIETH-CENTURY  OUTLOOK 

WE  have  seen  that  the  latter  half  of  the  nineteenth  cen- 
tury was  a  time  of  invention.  It  was  a  time  when  the 
great  discoveries  of  many  centuries  bore  fruit  in  great  in- 
ventions. It  was  thought  by  some  scientists  that  all  the 
great  discoveries  had  been  made,  and  that  all  that  remained 
was  careful  work  in  applying  the  great  principles  that  had 
been  discovered.  So  far  was  this  from  being  true  that  in 
the  last  ten  years  of  the  nineteenth  century  discoveries  were 
made  more  startling,  if  possible,  than  any  that  had  pre- 
ceded. The  nineteenth  century  not  only  brought  forth 
many  great  inventions,  but  handed  down  to  the  twentieth 
century  a  series  of  discoveries  that  point  the  way  to  still 
greater  inventions. 

Air-Ships 

For  centuries  men  sailed  over  the  water  at  the  mercy  of 
the  wind.  The  sailing  vessel  is  helpless  in  a  storm.  Early 
in  the  nineteenth  century  they  learned  to  use  the  power  of 
steam  for  ocean  travel,  and  the  wind  lost  its  terrors.  Late 
in  the  eighteenth  century  men  learned  to  sail  through  the 
air  in  balloons  even  more  at  the  mercy  of  the  wind  than  the 


THE  STORY  OF  GREAT  INVENTIONS 

sailing  vessels  on  the  ocean.  More  than  a  hundred  years 
later  they  learned  to  propel  air-ships  in  the  teeth  of  the 
wind.  The  nineteenth  century  saw  the  mastery  of  the 
water.  The  twentieth  is  witnessing  the  mastery  of  the  air. 

The  first  balloon  ascension  was  made  in  1783,  two  men 
being  carried  over  Paris  by  what  Benjamin  Franklin  called 
a  "bag  of  smoke."  The  balloon  was  a  bag  of  oiled  silk 
open  at  the  bottom.  In  the  middle  of  the  opening  was  a 
grate  in  which  bundles  of  fagots  and  sheaves  of  straw  were 
burned.  The  heated  air  filled  the  balloon,  and  as  the  heated 
air  was  lighter  than  the  air  around  it  the  balloon  could  rise 
and  carry  a  load.  Beneath  the  grate  was  a  wicker  car  for 
the  men.  They  were  supplied  with  straw  and  fagots  with 
which  to  feed  the  fire.  When  they  wanted  to  rise  higher 
thev  added  fuel  to  heat  the  air  in  the  balloon.  When  they 
wished  to  descend  they  allowed  the  fire  to  die  out,  so  that 
the  air  in  the  balloon  would  cool.  They  could  not  guide 
the  balloon,  but  drifted  with  the  wind.  That  great  philoso- 
pher Benjamin  Franklin,  who  saw  the  ascension,  said  that 
the  time  might  come  when  the  balloon  could  be  made  to 
move  in  a  calm  and  guided  in  a  wind.  In  the  second 
ascension  bags  of  sand  were  taken  as  ballast,  and  the  car 
was  suspended  from  a  net  which  enclosed  the  balloon.  In 
this  second  ascension  hydrogen  gas  was  used  in  place  of 
heated  air. 

The  greatest  height  ever  reached  by  a  human  being  is 
about  seven  miles.  This  height  was  first  reached  in  1862  by 
two  balloonists  who  nearly  lost  their  lives  in  the  adventure. 
At  a  height  of  nearly  six  miles  one  of  the  men  became  un- 
conscious. The  other  tried  to  pull  the  valve-cord  to  allow 

174 


THE   TWENTIETH-CENTURY   OUTLOOK 

the  gas  to  escape,  but  found  that  the  cord  was  out  of  his 
reach.  His  hands  were  frozen,  but  he  climbed  out  of  the 
car  into  the  netting  of  the  balloon,  secured  the  cord  in  his 
teeth,  returned  to  the  car,  and  threw  the  weight  of  his  body 
on  the  cord.  This  opened  the  valve  and  the  balloon  de- 
scended. 

Those  who  go  to  great  heights  now  provide  themselves 
with  tanks  of  compressed  oxygen.  Then  when  the  air 
becomes  so  thin  and  rare  that  breathing  is  difficult  they 
can  breathe  from  the  oxygen  tanks. 

A  captive  balloon  in  war  serves  as  an  observation  tower 
from  which  to  observe  the  enemy.  It  is  connected  to  the 
ground  by  a  cable.  This  cable  is  wound  on  a  drum  carried 
by  the  balloon  wagon.  The  balloon  can  be  lowered  or 
raised  by  winding  or  unwinding  the  cable. 

The  gas-bag  is  sometimes  made  of  oiled  silk,  sometimes 
of  two  layers  of  cotton  cloth  with  vulcanized  rubber  be- 
tween. The  cotton  cloth  gives  the  strength  needed,  and 
the  rubber  makes  the  bag  gas-tight. 

The  most  convenient  gas  for  rilling  balloons  is  heated  air, 
but  the  air  cools  rapidly  and  loses  its  lifting  power.  Coal- 
gas  furnished  by  city  gas-plants  is  sometimes  used.  This 
gas  will  lift  about  thirty-five  pounds  for  every  thousand 
cubic  feet.  A  balloon  holding  thirty-five  thousand  cubic 
feet  of  coal  gas  will  easily  lift  the  car  and  three  persons. 
The  lightest  gas  is  hydrogen.  This  gas  will  lift  about 
seventy  pounds  for  every  thousand  cubic  feet.  Hydrogen 
is  made  by  the  action  of  sulphuric  acid  and  water  on  iron. 
If  a  bit  of  iron  is  thrown  into  a  mixture  of  sulphuric  acid 
and  water  bubbles  of  hydrogen  gas  will  rise  through  the 
12 


THE    TWENTIETH-CENTURY   OUTLOOK 

liquid.  This  gas  will  burn  if  a  lighted  match  is  brought 
near. 

A  balloon  without  propelling  or  steering  apparatus  is  not 
an  air- ship.  It  may  be  raised  by  throwing  out  ballast  or 
lowered  by  letting  out  gas,  but  further  than  this  the  aero- 
naut has  no  control  over  its  movements.  The  balloon 
moves  with  the  wind.  No  breeze  is  felt,  for  balloon  and 
air  move  together.  To  the  aeronaut  the  balloon  seems  to 
be  in  a  dead  calm.  It  is  only  when  he  catches  sight  of 
houses  and  trees  and  rivers  darting  past  below  that  he 
realizes  that  the  balloon  is  moving. 

If  a  balloon  has  a  propelling  apparatus  it  may  move 
against  the  wind,  or  it  may  outspeed  the  wind.  A  balloon 
with  propelling  and  steering  apparatus  is  called  a  "dirigible" 
balloon,  which  means  a  balloon  that  can  be  guided.  Figs. 
89  and  90  are  from  photographs  of  a  "dirigible"  used  in  the 
British  army.  Such  a  balloon  is  usually  long  and  pointed 
like  a  spindle  or  a  cigar.  It  is  built  to  cut  the  air,  just  as  a 
rowboat  built  for  speed  is  long  and  pointed  so  that  it  may 
cut  the  water.  The  propeller  acts  like  an  electric  fan.  An 
electric  fan  drives  the  air  before  it,  but  the  air  pushes  back 
on  the  fan  just  as  much  as  the  fan  pushes  forward  on  the 
air,  and  if  the  fan  were  suspended  by  a  long  cord  it  would 
move  backward.  So  the  large  fan  or  screw  propeller  on  an 
air-ship  drives  the  air  backward,  and  the  air  reacts  and 
drives  the  ship  forward.  In  the  same  way  the  screw- 
propeller  of  an  ocean  liner  drives  the  vessel  forward  by  the 
reaction  of  the  water. 

A  balloon  rises  for  the  same  reason  that  wood  floats  on 
water.  The  wood  is  lighter  than  water,  and  the  water 

177 


THE   TWENTIETH-CENTURY   OUTLOOK 

holds  it  up.  The  balloon  is  lighter  than  air  and  the  air 
pushes  it  up.  The  upward  push  of  the  air  is  just  equal  to 
the  weight  of  the  air ,  that  would  fill  the  same  space  the 
balloon  fills.  The  balloon  can  support  a  load  that  makes 
the  whole  weight  of  the  balloon  and  its  load  together  equal 
to  the  weight  of  the  air  that  would  fill  the  same  space.  For 
the  balloon  to  rise  the  load  must  be  somewhat  lighter  than 
this.  A  balloon  may  be  made  lighter  than  air  by  filling 
it  with  heated  air  or  coal-gas.  Hydrogen,  however,  is  used 
in  the  better  balloons  and  in  air-ships  of  the  "lighter  than 
air"  type. 

The  air- ship  must,  of  course,  use  a  very  light  motor.  A 
steam-engine  cannot  .be  made  light  enough.  Neither  can 
an  electric  motor,  if  we  add  the  weight  of  the  storage  battery 
that  would  be  required.  Air-ships  have  been  propelled  by 
both  steam-engines  and  electric  motors,  but  with  low  speed 
because  of  the  weight  of  the  engine  or  motor.  The  only 
successful  motor  for  this  purpose  is  the  gasolene  motor, 
which  is  a  form  of  gas-engine  using  gas  formed  by  the 
evaporation  of  gasolene. 

The  first  air-ship  that  could  be  controlled  and  brought 
back  to  the  starting-point  was  made  in  France,  in  1885,  by 
Captain  Renard,  of  the  French  army.  It  was  a  cigar- 
shaped  balloon,  with  a  screw  propeller  run  by  an  electric 
motor  of  eight  horse-power.  The  ship  attained  a  speed  of 
thirteen  miles  an  hour. 

A  more  successful  air-ship  was  that  built  by  Santos 
Dumont.  With  this  ship,  in  1901,  he  won  a  prize  of  $20,000, 
which  had  been  offered  to  the  builder  of  the  first  air-ship  that 
would  sail  round  the  Eiffel  Tower  in  Paris  from  the  Aero- 

179 


THE  STORY  OF  GREAT  INVENTIONS 


static  Park  of  Vaugirard,  a  distance  of  about  three  miles, 
and  return  in  half  an  hour. 

The  balloon  part  of  this  air-ship  was  112^  feet  long  and 
19 J  feet  in  diameter,  holding  about  6400  cubic  feet  of  gas. 
The  car  was  built  of  pine  beams  no  larger  in  section  than 
two  fingers  and  weighing  only  no  pounds.  This  car  could 
be  taken  apart  and  put  in  a  trunk.  A  gasolene  automobile 
motor  was  used,  and  thus  it  is  seen  that  the  automobile 
aided  in  solving  the  problem  of  sailing  through  the  air.  It 
was  the  automobile  that  led  to  the  construction  of  light  and 
powerful  gasolene  motors.  The  car  and  motor  were  sus- 
pended from  the  balloon  by  means  of  piano  wires,  which 
at  a  short  distance  were  invisible,  so  that  the  man  in  the 
car  appeared  in  some  mysterious  way  to  follow  the  balloon. 
The  ship  was  turned  to  the  left  or  right  by  means  of  a 
rudder.  It  was  made  to  ascend  or  descend  by  shifting  the 
weight  of  a  heavy  rope  that  hung  from  the  car,  thus  in- 
clining the  ship  upward  or  downward. 

Count  Zeppelin,  of  Germany,  constructed  a  much  larger 
dirigible  balloon  than  that  of  Santos  Dumont.  The  balloon 
of  the  first  Zeppelin  air- ship  w^as  390  feet  in  length,  with  a 
diameter  of  about  39  feet.  It  was  divided  into  seventeen 
sections,  each  section  being  a  balloon  in  itself.  These  sec- 
tions serve  the  same  purpose  as  the  water-tight  compart- 
ments of  a  battle-ship.  An  accident  to  one  section  would 
not  mean  the  destruction  of  the  entire  ship.  Within  the 
balloon  is  a  framework  of  aluminum  rods  extending  from 
one  end  to  the  other  and  held  in  place  by  aluminum  rings 
twenty-four  feet  apart.  The  balloon  contains  about  108,000 
cubic  feet  of  gas,  and  it  costs  about  $2500  to  fill  it.  One 

1 80 


FIG.    91 A    ZEPPELIN    AIR-SHIP 


THE  STORY  OF  GREAT  INVENTION S 

filling  of  gas  will  last  about  three  weeks.  There  are  two 
cars,  each  about  ten  feet  long,  five  feet  wide,  and  three  feet 
deep.  The  cars  are  connected  by  a  narrow  passageway 
made  of  aluminum  wires  and  plates,  making  a  walking 
distance  of  326  feet — longer  than  the  decks  of  many  ocean 
steamers.  A  sliding  weight  of  300  kilograms  (about  600 
pounds)  serves  the  same  purpose  as  the  guide-ropes  in  the 
Santos  Dumont  air- ship.  By  moving  this  weight  forward 
or  backward  the  ship  is  raised  or  lowered  at  the  bow  or 
stern,  and  thus  caused  to  glide  up  or  down.  Anchor-ropes 
are  carried  for  use  in  landing.  The  ship  is  propelled  by 


4   t 


FIG.     92 COUNT     ZEPPELINS         DEUTSCHLAND,         THE     FIRST     AIR-SHIP     IN 

REGULAR    PASSENGER    SERVICE 

182 


THE   TWENTIETH-CENTURY   OUTLOOK 


four  screws,  and  guided  by  a  number  of  rudders  laced 
some  in  front  and  some  in  the  rear.  The  first  Zeppelin 
air- ship  carried  four  passengers.  The  work  of  Dumont  and 


Copyright  by  Pictorial  News  Co. 
FIG.    93 THE    BALDWIN    AIR-SHIP    USED    IN    THE    UNITED    STATES    ARMY 

Zeppelin  has  led  the  great  powers  to  manufacture  dirigible 
balloons  for  use  in  time  of  war.  Fig.  91  shows  one  of  the 
Zeppelin  air-ships  sailing  over  a  lake. 

A  larger  air-ship,  the  Deutschland,  built  later  by  Count 
Zeppelin,  was  the  first  air-ship  to  be  used  for  regular  pas- 
senger service.  The  Deutschland  is  shown  in  Fig.  92.  The 
Deutschland  carried  the  crew  and  twenty  passengers.  It 

183 


THE  STORY  OF  GREAT  INVENTIONS 

operated  for  a  time  as  a  regular  passenger  air-ship  between 
Friedrichshafen  and  Dusseldorf ,  a  distance  of  three  hundred 
miles.  The  Deutschland  was  wrecked  in  a  storm  on  June  28, 
1910,  but  it  was  successfully  operated  long  enough  to  give 
Germany  the  honor  of  establishing  the  first  air-ship  line  for 
regular  passenger  service.  This  is  an  honor  perhaps  equal- 
ly as  great  as  that  of  establishing  the  first  commercial  elec- 
tric railway,  which  also  belongs  to  Germany.  An  American 
army  air-ship  is  shown  in  Fig.  93. 

The  Aeroplane 

The  aeroplane  is  a  later  development  than  the  dirigible 
balloon.  The  aeroplane  is  heavier  than  air.  So  is  a  bird 
and  so  is  a  kite.  What  supports  a  kite  or  a  bird  as  it  soars  ? 
Every  boy  knows  that  the  strings  of  a  kite  must  be  attached 
so  that  the  kite  is  inclined  and  catches  the  wind  under- 
neath. Then  the  wind  lifts  the  kite.  In  still  air  the  kite 
will  not  fly  unless  the  boy  who  holds  the  string  runs  very 
fast  and  so  causes  an  artificial  breeze  to  blow  against  the 
kite.  In  much  the  same  way  a  hovering  bird  is  held  aloft 
by  the  wind.  In  a  dead  calm  the  bird  must  flap  its  wings 
to  keep  afloat.  If  the  kite  string  is  cut  the  kite  tips  over 
and  drops  to  the  earth  because  it  has  lost  its  balance.  The 
lifting  power  of  the  wind  is  well  shown  in  the  man-lifting 
kites  which  are  used  in  the  British  army  service.  In  a  high 
wind  a  large  kite  is  used  in  place  of  a  captive  balloon.  It 
is  a  box -kite  made  of  bamboo  and  carries  a  passenger  in  a 
car,  the  car  running  on  the  cable  which  attaches  the  kite 
to  the  ground.  Now  suppose  a  kite  with  a  motor  and  pro- 

184 


FIG.    94 — IN    FULL    FLIGHT 


THE  STORY  OF  GREAT  INVENTIONS 

peller  in  place  of  a  string  and  a  boy  to  run  with  it,  and  that 
the  kite  is  able  to  balance  itself,  then  it  will  sail  against  a 
wind  of  its  own  making  and  you  have  a  flying-machine 
heavier  than  air. 

The  first  aeroplane  that  would  fly  under  perfect  control 
of  the  operator  was  built  by  the  Wright  brothers  at  Dayton, 
Ohio.  When  they  were  boys,  Bishop  Wright  gave  his  two 
sons,  Orville  and  Wilbur,  a  toy  flyer.  From  that  time  on 
the  thought  of  flying  through  the  air  was  in  their  minds. 
A  few  years  later  the  death  of  Lilienthal,  who  was  killed  by 
a  fall  with  his  glider  in  Germany,  stirred  them,  and  they 
took  up  the  problem  in  earnest.  They  read  all  the  writings 
of  Lilienthal  and  became  acquainted  with  Mr.  Octave 
Chanute,  an  engineer  of  Chicago  who  had  made  a  success- 
ful glider.  They  soon  built  a  glider  of  their  own,  and  ex- 
perimented with  it  each  summer  on  the  huge  sand-dunes  of 
the  North  Carolina  coast. 

A  glider  is  an  aeroplane  without  a  propeller.  With  it 
one  can  cast  off  into  the  air  from  a  great  height  and  sail 
slowly  to  the  ground.  Before  attempting  to  use  a  motor 
and  propeller,  the  Wrights  learned  to  control  the  glider 
perfectly.  They  had  to  learn  how  to  prevent  its  being 
tipped  over  by  the  wind,  and  how  to  steer  it  in  any  direc- 
tion. This  took  years  of  patient  work.  But  the  problem 
was  conquered  at  last,  and  they  attached  a  motor  and  pro- 
peller to  the  glider,  and  had  an  air-ship  under  perfect  con- 
trol and  with  the  speed  of  an  express- train.  Their  flyer 
of  1905,  which  made  a  flight  of  twenty-four  miles  at  a  speed 
of  more  than  thirty-eight  miles  an  hour,  carried  a  twenty- 
five-horse-power  gasolene  motor,  and  weighed,  with  its  load, 

186 


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THE  STORY  OF  GREAT  INVENTIONS 


925  pounds.     Figs.  94  and  95  show  the  Wright  air-ship  in 
flight.     Fig.  97  shows  the  mechanism. 

How  the  Wright  Aeroplane  Is  Kept  Afloat 

The  Wright  aeroplane  is  balanced  by  a  warping  or  twist- 
ing of  the  planes  i  and  2,  which  form  the  supporting  sur- 
faces (Fig.  96) .  If  left  to  itself  the  machine  would  tip  over 
like  a  kite  when  the  string  is  cut  and  drop  edgewise  to 
the  ground.  Suppose  the  side  R  starts  to  fall.  The  cor- 
ners a  and  e  are  raised  by  the  operator  while  b  and  /  are 
lowered,  thus  twisting  the  planes,  as  shown  in  the  dotted 
lines  of  the  figure.  The  side  R  then  catches  more  wind  than 
the  side  L.  The  wind  exerts  a  greater  lifting  force  on  R  than 
on  L,  and  the  balance  is  restored.  The  twist  is  then  taken 
out  of  the  machine  by  the  operator.  A  ship  when  sailing 
on  an  even  keel  presents  true  un warped  planes  to  the  wind. 

The  twisting  is  brought  about  by  a  pull  on  the  rope  3, 
which  is  attached  at  d  and  c,  and  passes  through  pulleys  at 
g  and  h.  When  the  rope  is  pulled  toward  the  left  the  right 
end  is  tightened  and  slack  is  paid  out  at  the  left  end.  This 
pulls  down  the  corner  d,  and  raises  e.  The  corner  a  is 
raised  by  the  post  which  connects  a  and  e.  The  rope  4, 
passing  from  a  to  b  through  pulleys  at  m  and  n,  is  thus 
drawn  toward  a  and  pulls  down  the  corner  b.  Thus  a  is 
raised  and  b  is  lowered.  At  the  same  time  rope  4  turns 
the  rear  rudder  to  the  left,  as  shown  by  the  dotted  lines, 
thus  forcing  the  side  R  against  the  wind.  Of  course,  if 
the  left  side  of  the  machine  starts  to  fall,  the  rope  3  is 
pulled  toward  the  right,  and  all  the  movements  take  place 

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THE  STORY  OF  GREAT  INVENTIONS 

in  the  opposite  direction.  The  ropes  are  connected  to  a 
lever,  by  which  the  operator  controls  the  warping  of  the 
planes.  These  movements  are  possible  because  the  joints 
are  all  universal,  permitting  movement  in  any  direction. 
In  whatever  position  the  planes  may  be  set,  they  are  held 
perfectly  rigid  by  the  two  ropes,  together  with  others  not 
shown  in  the  figure.  The  machine  is  guided  up  or  down 
by  the  front  horizontal  rudder. 

When  the  aeroplane  swings  round  a  curve  the  outer  wing 
is  raised  because  it  moves  faster  than  the  inner  wing,  and 
therefore  has  greater  lifting  force.  Thus  the  aeroplane  banks 
its  own  curves. 

The  Wright  flying-machine  is  called  a  biplane  because  it 
has  two  principal  planes,  one  above  the  other.  A  number  of 
successful  flying-machines  have  been  built  with  only  one 
plane,  and  these  are  called  monoplanes.  A  monoplane  that 
early  became  famous  is  that  of  Bleriot  (Fig.  98).  The 
Bleriot  monoplane  was  the  first  flying-machine  to  cross  the 
English  Channel.  This  machine  is  controlled  by  a  single 
lever  mounted  with  a  ball-and-socket  coupling,  so  that  it 
can  move  in  any  direction.  When  on  the  ground  it  is  sup- 
ported by  three  wheels  like  bicycle  wheels,  so  that  it  does 
not  require  a  track  for  starting,  but  can  start  anywhere  from 
level  ground.  The  Wright  and  the  Bleriot  represent  the 
two  leading  types  of  early  successful  flying-machines. 

Submarines 

Successful  navigation  beneath  the  surface  of  the  water, 
though  not  carried  to  the  extent  imagined  by  Jules  Verne, 

190 


I  S 

^   o 


THE  STORY  OF  GREAT  INVENTIONS 


was  a  reality  at  the  beginning  of  the  twentieth  century. 
Instead  of  twenty  thousand  leagues  under  the  sea,  less 
than  a  hundred  leagues  had  been  accomplished,  but  no  one 
can  foretell  what  the  future  may  have  in  store. 

The  principal  use  of  the  submarine  is  in  war.     It  is  a 
diving  torpedo  -  boat,   and  acts  under  cover  of  water  as 


Copyright  by  M.  Brauger,   Paris 

FIG.  98 — THE  BL£RIOT  MONOPLANE 


the  light  artillery  on  land  is  secured  behind  intrenchments. 
The  weapon  used  by  the  submarine  is  the  torpedo.  The 
torpedo  is  itself  a  small  submarine  able  to  propel  itself,  and 
if  started  in  the  water  toward  a  certain  object,  to  go  under 
water  straight  to  the  mark.  It  carries  a  heavy  charge  either 

192 


THE   TWENTIETH-CENTURY   OUTLOOK 

of  guncotton  or  dynamite,  which  explodes  when  the  tor- 
pedo strikes  a  solid  object,  such  as  a  battle-ship.  The  first 
torpedo  was  intended  to  be  steered  from  the  shore  by  means 
of  long  tiller-ropes,  and  to  be  propelled  by  a  steam-engine 
or  by  clockwork.  The  Whitehead  fish  torpedo,  invented 
in  1866,  is  self-steering.  At  the  head  of  the  torpedo  is  a 
pointed  steel  firing-pin.  When  the  torpedo  strikes  a  ship 
or  any  rigid  object  this  steel  pin  is  driven  against  a  det- 
onator cap  which  is  in  the  centre  of  the  charge  of  dyna- 
mite. The  blow  causes  the  cap  to  explode,  and  the  ex- 
plosion of  the  cap  explodes  the  dynamite.  The  torpedo  is 
so  arranged  that  it  cannot  explode  until  it  is  about  thirty 
yards  away  from  the  ship  from  which  it  is  fired.  The  steel 
pin  cannot  strike  the  cap  until  a  small  " collar"  has  been 
revolved  off  by  a  propeller  fan,  and  this  requires  a  distance 
of  about  thirty  yards.  The  screw  propeller  is  driven  by 
compressed  air.  A  valve  which  is  worked  by  the  pressure 
of  the  water  keeps  the  torpedo  at  any  depth  for  wjaich  the 
valve  is  set.  The  torpedo  contains  many  ingenious  devices 
for  bringing  it  quickly  to  the  required  depth  and  keeping 
it  straight  in  its  course.  One  of  these  devices  is  the  gyro- 
scope, which  will  be  described  under  the  head  of  ''spinning 
tops."  Whitehead  torpedoes  are  capable  of  running  at  a 
speed  of  over  thirty-seven  miles  an  hour  for  a  range  of  two 
thousand  yards  and  hitting  the  mark  aimed  at  almost  as 
accurately  as  a  gun.  The  submarine  boat  carries  a  number 
of  torpedoes,  and  has  one  torpedo-tube  near  the  forward 
end  from  which  to  fire  the  torpedoes. 

It  would  be  very  difficult  for  one  submarine  to  fight  an- 
other submarine,  for  the  submarine  when  completely  sub- 

i93 


THE  STORY  OF  GREAT  INVENTIONS 

merged  is  blind.  It  could  not  see  in  the  water  to  find  its 
enemy.  The  torpedo-boat-destroyer  is  able  to  destroy  a 
submarine  by  means  of  torpedoes,  shells  full  of  high  ex- 
plosives, or  quick-firing  guns.  Advantage  must  be  taken 
of  the  moment  when  the  submarine  comes  to  the  surface 
to  get  a  view  of  her  enemy. 

One  of  the  great  enemies  of  the  submarine  will  probably 
be  the  air- ship,  for  while  the  submarine  when  under  water 
cannot  be  seen  from  a  ship  on  the  surface,  it  can,  under 
favorable  conditions,  be  seen  from  a  certain  height  in  the 
air. 

Most  submarines  use  a  gasolene  motor  for  surface  travel, 
and  an  electric  motor  run  by  a  storage  battery  for  naviga- 
tion below  the  surface.  The  best  submarines  can  travel  at 
the  surface  like  an  ordinary  boat,  or  "  awash  "  —that  is,  just 
below  the  surface — with  only  the  conning  tower  projecting 
above  the  water,  or  they  can  travel  completely  submerged. 

The  rising  and  sinking  of  the  submarine  depend  on  the 
principle  of  Archimedes.  The  upward  push  of  the  water  is 
just  equal  to  the  weight  of  the  water  displaced.  If  the 
water  displaced  weighs  more  than  the  boat,  then  the  up- 
ward push  of  the  water  is  greater  than  the  weight  of  the 
boat  and  the  boat  rises.  However,  the  boat  can  be  made 
to  dive  when  its  weight  is  just  a  little  less  than  the  weight 
of  the  water  displaced.  This  is  done  by  means  of  horizon- 
tal rudders  which  may  be  inclined  so  as  to  cause  the  boat 
to  glide  downward  as  its  propeller  drives  it  forward. 

The  magnetic  compass  is  not  reliable  in  a  submarine  with 
a  hull  made  of  steel.  The  electric  motor  used  for  propel- 
ling the  boat  under  water  also  interferes  with  the  action  of 

194 


THE   TWENTIETH-CENTURY   OUTLOOK 

the  compass,  because  of  its  magnetic  field.  The  gyroscope, 
which  we  shall  describe  later,  is  not  affected  by  magnetic 
action,  and  may  take  the  place  of  the  compass. 

Water  ballast  is  used,  and  when  the  submarine  wishes  to 
dive,  water  is  admitted  into  the  tanks  until  the  boat  is 
nearly  heavy  enough  to  sink  of  its  own  weight.  It  is  then 
guided  downward  by  the  horizontal  rudder.  The  sub- 
marine is  driven  by  a  screw  propeller,  and  some  submarines 
are  lowered  by  means  of  a  vertical  screw.  Just  as  a  hori- 
zontal screw  propels  a  vessel  forward,  so  a  vertical  screw 
will  propel  it  downward.  When  the  submarine  wishes  to 
rise,  it  may  do  so  by  the  action  of  its  rudder,  or  the  water 
may  be  pumped  out  of  its  tanks,  when  the  water  will  raise 


FIG.  99 — THE  "PLUNGER" 

Photo  by  Pictorial  News  Co. 
195 


THE  STORY  OF  GREAT  INVENTIONS 

it  rapidly.  A  submarine  which  is  kept  always  a  little 
lighter  than  water  will  rise  to  the  surface  in  case  of  accident 
to  its  machinery.  Figs.  99,  100,  and  101  are  from  photo- 
graphs of  United  States  submarines. 

There  is  one  kind  of  submarine  built  for  peaceful  pur- 
suits which  deserves  mention.  It  is  the  Argonaut,  invented 
by  Simon  Lake.  This  remarkable  boat  crawls  along  the 
bottom  of  the  sea,  but  not  at  a  very  great  depth.  It  is 
equipped  with  divers'  appliances,  and  is  used  in  saving 
wreckage.  Divers  can  go  out  through  the  bottom  of  the 
boat,  walk  about  on  the  sea  bottom,  and  when  through  with 
their  work  re-enter  the  boat;  all  the  while  boat  and  men 
are,  perhaps,  a  hundred  feet  below  the  surface.  The  divers' 
compartment,  from  which  the  divers  go  out  into  the  water, 
is  separated  by  an  air-tight  partition  from  the  rest  of  the 
boat.  Compressed  air  is  forced  into  this  compartment  until 
the  pressure  of  the  air  equals  the  pressure  of  the  water  out- 
side. Then  the  door  in  the  bottom  is  opened,  and  the  air 
keeps  the  water  out.  The  men  in  their  diving-suits  can 
then  go  out  and  in  as  they  please. 

For  every  boat  there  is  a  depth  beyond  which  it  must 
not  go.  The  penalty  for  going  beyond  this  depth  is  a 
batter ed-in  vessel,  for  the  pressure  increases  with  the  depth. 
Every  time  the  depth  is  increased  thirty-two  feet  the  press- 
ure is  increased  fifteen  pounds  on  every  square  inch.  Be- 
yond a  certain  depth  the  vessel  cannot  resist  the  pressure. 
Submarines  have  been  made  strong  enough  to  withstand 
the  pressure  at  a  depth  of  five  thousand  feet,  or  nearly  a 
mile.  Most  submarines,  however,  cannot  go  deeper  than 
a  hundred  and  fifty  feet. 

196 


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THE  STORY  OF  GREAT  INVENTIONS 

Air  is  supplied  to  the  occupants  of  the  boat  either  from 
reservoirs  containing  compressed  air  or  oxygen,  or  by  means 
of  chemicals  which  absorb  the  carbon  dioxide  produced  in 
breathing  and  restore  the  needed  quantity  of  oxygen  to  the 
air. 

While  the  men  in  >the  boat  cannot  see  in  the  water,  they 
can  see  objects  on  the  surface  of  the  water,  even  when  their 


FIG.    101 FIRST    SUBMARINE    CONSTRUCTED    IN    UNITED    STATES.        IT    WENT 

TO    THE     BOTTOM    WITH     SEVEN    MEN,    WHO    WERE    DROWNED 

Photo  by  Pictorial  News  Co. 

boat  is  several  feet  below  the  surface,  by  means  of  the  peri- 
scope. This  is  an  arrangement  of  lenses  and  mirrors  in  a 
tube  bent  in  two  right  angles,  which  projects  a  short  dis- 
tance above  the  surface  and  can  be  turned  in  any  direction 

198 


THE    TWENTIETH-CENTURY   OUTLOOK 


(Fig.  102).  Thus  the  boat, 
while  itself  nearly  invisible, 
can  have  a  clear  view  of  the 
battle-ship  which  it  is  about 
to  attack. 

Some  Spinning  Tops   that 
Are  Useful 

Every  one  knows  that  a 
top  will  stand  upright  only 
when  it  is  spinning.  Most 
tops  when  spinning  will 
stand  very  rough  treatment 
without  being  upset.  The 
whip -top  will  stand  a  se- 
vere lashing.  Spin  a  top 
upright  and  give  it  a  knock. 
It  will  go  round  in  a  circle 
in  a  slanting  position,  and 
after  a  time  will  right  itself. 
If  the  top  is  struck  toward 
the  south  it  will  not  bow- 
to  ward  the  south,  but  tow- 
ard the  east  or  west.  In 
throwing  a  quoit,  the  quoit 

must  be  given  a  spinning  motion  or  the  thrower  cannot  be  cer- 
tain how  it  will  alight.  A  coin  thrown  up  with  a  spinning  mo- 
tion will  not  turn  over.  The  quoit  and  the  coin  are  like  the 
top.  They  will  not  turn  over  easily  when  spinning.  For 
the  same  reason  a  rifle  bullet  is  set  spinning  by  the  spiral 

199 


FIG.  102 HOW  MEN  IN  A  SUBMARINE 

SEE    WHEN    UNDER    THE    WATER 


THE  STORY  OF  GREAT  INVENTIONS 

grooves  in  the  bore  of  the  gun,  and  it  goes  straight  to  its 
mark.  With  a  smooth-bore  gun  that  does  not  set  the  bullet 
spinning  the  gunner  cannot  be  sure  of  his  aim. 

It  took  a  long  time  to  discover  that  the  spinning  top  is 
a  useful  machine.  It  is  useful  because  of  its  steady  motion, 
because  it  is  difficult  to  turn  over.  It  was  discovered  by 
Newton  long  ago  that  every  moving  object  tries  to  keep 
on  in  the  direction  in  which  it  is  moving.  A  moving  object 
always  requires  some  force  to  change  its  direction.  The 
spinning  top  is  a  beautiful  illustration  of  this  principle. 
The  top  that  is  most  useful  is  the  gyroscope  top  (Fig.  103). 
It  is  mounted  on  pivots  so  arranged  that  the  top  can  turn  in 
any  direction  within  the  frame  that  supports  it.  If  the 
top  is  set  spinning  one  may  turn  the  frame  in  any  direction, 


FIG.    103 A    TOP    THAT    SPINS    ON    A    STRING 

but  the  top  does  not  change  direction.  The  axis  of  the  top 
will  point  in  the  same  direction  all  the  while  the  top  is 
spinning,  no  matter  how  the  supporting  frame  is  moved 
about.  The  top  will  spin  on  a  string.  If  attached  inside 

200 


THE   TWENTIETH-CENTURY   OUTLOOK 

a  box  the  box  can  be  made  to  stand  on  one  corner  while  the 
top  is  spinning. 

This  top,  which  is  so  hard  to  upset,  has  been  used  in  ships 
to  prevent  the  ship  being  rolled  by  the  waves.  A  large  fly- 
wheel is  mounted  in  the  middle  of  the  vessel  on  a  hori- 
zontal axle.  A  fly-wheel  is  only  a  large  top.  It  spins  with 
a  steady  motion,  and  because  of  its  larger  size  it  is  very 
much  harder  to  overturn  than  a  toy  top.  The  fly-wheel  in 
the  ship  resists  the  rolling  force  of  the  waves  and  steadies 
the  ship,  so  that  even  with  high  waves  the  rolling  can 
scarcely  be  felt.  The  waves  do  not  so  readily  break  over 
the  ship  when  thus  steadied  by  the  revolving  wheel. 

The  gyroscope  is  also  used  in  some  forms  of  torpedo  to 
give  the  torpedo  steady  motion.  By  means  of  a  spring  re- 
leased by  a  trigger  the  gyroscope  within  the  torpedo  is  set 
spinning  before  the  torpedo  enters  the  water.  The  gyro- 
scope keeps  its  direction  unchanged,  and  as  the  torpedo 
turns  one  way  or  the  other  the  gyroscope  acts  upon  one  or 
the  other  of  two  valves  connected  with  the  compressed-air 
chambers  from  which  the  screws  of  the  torpedo  are  driven. 
The  air  thus  set  free  by  the  gyroscope  drives  a  piston-rod 
connected  with  a  rudder  in  such  a  way  as  to  right  the  tor- 
pedo. The  torpedo  goes  through  the  water  with  a  slightly 
zigzag  motion,  but  never  more  than  two  feet  out  of  the  line 
in  which  it  was  aimed. 

The  Monorail-Car 

Another  use  of  the  gyroscope  is  in  the  monorail-car.  To 
make  a  car  run  on  a  single  rail,  with  its  weight  above  the 

201 


THE  STORY  OF  GREAT  INVENTIONS 

rail,  was  impossible  until  the  use  of  the  gyroscope  was  dis- 
covered. In  the  monorail-car  invented  by  Brennan  (Fig. 
104)  there  are  two  gyroscopes,  each  weighing  fifteen  hun- 
dred pounds,  driven  at  a  speed  of  three  thousand  revolu- 
tions a  minute  by  an  electric  motor.  Each  gyroscope  wheel 


FIG.     104 A    CAR    THAT    RUNS    ON    ONE    RAIL 

Louis  Brennan's  full-size  monorail. 


with  its  motor  is  mounted  in  an  air-tight  casing  from  which 
the  air  is  pumped  out.  The  wheel  will  run  much  more  easily 
in  a  vacuum  than  in  air,  for  the  air  offers  very  great  resist- 
ance to  its  motion.  The  wheels  are  placed  one  on  each  side 
of  the  car  with  their  axles  horizontal.  When  the  car  starts 
to  fall  the  spinning  gyroscopes  right  it  much  as  a  spinning 
top  rights  itself  if  tipped  to  one  side  by  a  blow.  If  the  wind 
tips  the  car  to  the  left  the  gyroscopes  incline  to  the  right 

202 


THE   TWENTIETH-CENTURY   OUTLOOK 

until  the  car  is  again  upright.  If  the  load  is  heavier  on  the 
right  side  the  car  inclines  itself  toward  the  left  just  as  a 
man  leans  to  the  left  when  carrying  a  load  on  his  right 
shoulder.  In  rounding  a  curve  the  car  leans  to  the  inside 
of  the  curve  just  as  a  bicycle  rider  does,  and  as  a  railway 
train  is  made  to  do  by  laying  the  outer  rail  of  the  curve 
higher  than  the  inner  rail.  Two  gyroscopes  spinning  in 
opposite  directions  are  necessary  to  keep  the  car  from  fall- 
ing when  rounding  a  curve. 

The  gyroscope  may  be  used  in  place  of  a  compass.  If  it 
is  set  spinning  in  a  north  and  south  direction  it  will  con- 
tinue to  spin  in  a  north  and  south  direction,  no  matter  how 
the  ship  may  turn.  It  is  even  more  reliable  than  the  com- 
pass, for  it  is  not  affected  by  magnetic  action.  Possibly 
some  of  the  great  inventions  yet  to  be  made  will  be  new 
uses  of  the  spinning  top. 

Liquid  Air  and  the  Greatest  Cold 

For  a  long  time  after  men  had  learned  the  use  of  the  fur- 
nace and  could  produce  great  heat,  the  greatest  cold  known 
was  that  of  the  mountain-top.  Men  wondered  what  would 
happen  if  air  could  be  made  colder  than  the  frost  of  winter, 
but  knew  not  how  to  bring  about  such  a  result.  They  won- 
dered what  things  could  be  frozen  that  remain  liquid  or 
gaseous  even  in  the  cold  of  winter. 

The  first  artificial  cold  was  produced  by  a  mixture  of 
salt  and  ice,  such  as  we  now  use  in  an  ice-cream  freezer. 
In  time  men  learned  other  ways  of  producing  great  cold 
and  even  to  manufacture  ice  in  large  quantities. 

203 


THE  STORY  OF  GREAT  INVENTIONS 


The  cold  of  liquid  air  is  far  greater  than  that  of  ice  or 
even  a  freezing  mixture  of  salt  and  ice.  Liquid  air  is  simply 
air  that  is  so  cold  that  it  becomes  a  liquid  just  as  steam 
when  cooled  forms  water.  Steam  has  only  to  be  cooled  to 
the  temperature  of  boiling  water,  while  air  must  be  cooled 
to  314  degrees  below  zero  on  the  Fahrenheit  scale. 

If  it  were  possible  for  us  to  live  in  such  a  climate,  and 
tfye  world  were  cooled  to  the  temperature  of  liquid  air,  we 
should  have  a  curious  world,  \yatch  -  springs  might  be 
made  out  of  pewter,  bells  of  tin,  and  piano  wires  of  solder, 
for  these  metals  are  made  stronger  by  the  extreme  cold  of 
liquid  air.  There  would  be  no  air  to  breathe.  Oceans  and 
rivers  would  be  frozen  solid,  and  the  air  would  form  a  liquid 
ocean  about  thirty-five  feet  deep.  This  ocean  of  liquid  air 
would  be  kept  boiling  a  long  time  by  the  heat  of  the  ice 
beneath  it,  for  ice  is  hot  compared  with  liquid  air.  The  ice 
would  cool  as  it  gave  up  its  heat  to  the  liquid  air  and  in 
time  become  as  cold  as  the  liquid  air  itself. 

Liquid  air  has  been  shipped  thousands  of  miles  in  a  double 
walled  tin  can,  the  space  between  the  two  walls  being  filled 
with  felt.  The  felt  protects  the  liquid  air  from  the  Jieat  of 
the  air  without.  The  liquid  air  evaporates  slowly,  and  es- 
capes through  a  small  opening  at  the  top. 

Professor  Dewar,  a  successor  of  Faraday  in  the  Royal 
Institution,  invented  the  Dewar  bulb,  by  means  of  which 
the  evaporation  of  the  liquid  air  is  prevented.  This  bulb 
is  a  double- walled  flask.  In  the  space  between  the  two 
walls  of  the  flask  is  a  vacuum.  Now  a  vacuum  is  the  best 
possible  protection  against  heat.  If  we  were  to  take  a 
bottle  full  of  air  and  pump  out  from  the  bottle  all  except 

204 


THE   TWENTIETH-CENTURY   OUTLOOK 

about  a  thousandth  of  a  millionth  of  the  air  it  contained  at 
first  we  should  have  such  a  vacuum  as  that  of  the  Dewar 
bulb.  With  such  a  vacuum  around  it  ice  could  be  kept 
from  melting  for  many  days  even  in  the  hottest  weather, 
for  no  heat  can  go  through  a  vacuum. 

But  the  greatest  cold  is  not  the  cold  of  liquid  air.  Liquid 
hydrogen  is  so  cold  that  it  freezes  air.  When  a  flask  of 
liquid  hydrogen  is  opened  there  is  a  small  snow-storm  of 
frozen  air  in  the  mouth  of  the  flask.  But  even  this  is  not 
the  greatest  cold.  The  liquid  hydrogen  may  be  frozen, 
forming  a  hydrogen  snow  whose  temperature  is  43  5  degrees 
below  zero.  This  is  nearly  equal  to  the  cold  of  the  space 
beyond  the  earth's  atmosphere,  which  is  the  greatest  pos- 
sible cold. 

The  Electric  Furnace  and  the  Greatest  Heat 

The  greatest  heat  that  has  yet  been  produced  artificially 
is  that  of  the  electric  arc.  The  exact  temperature  of  the 
electric  arc  is  not  known  with  certainty.  It  is  known,  how- 
ever, that  the  temperature  of  the  hottest  part  of  the  arc 
is  not  less  than  6500  degrees  Fahrenheit.  When  we  com- 
pare this  with  the  temperature  of  the  hottest  coal  furnace, 
which  is  about  4000  degrees,  we  can  very  easily  understand 
that  something  is  likely  to  happen  at  the  temperature  of 
the  electric  arc  that  could  not  happen  in  an  ordinary 
furnace. 

If  an  electric  arc  is  enclosed  by  something  that  will  hold 
the  heat  in  we  have  an  electric  furnace,  and  any  substance 
placed  in  the  furnace  may  be  made  nearly  as  hot  as  the 

205 


THE  STORY  OF  GREAT  INVENTIONS 

arc  itself.  In  the  electric  furnace  any  substance,  whether 
found  in  nature  or  prepared  artificially,  may  be  melted  or 
vaporized. 

It  was  Henri  Moissan,  Professor  of  Chemistry  at  the  Sor- 
bonne  in  Paris,  who  made  the  first  great  discoveries  in  the 
use  of  the   electric   furnace   and  produced   the  first  artifi- 
cial diamonds.     The  study  of  diamonds  led  Moissan  to  be- 
lieve that  in  nature  they  are  formed  by  the  cooling  of  a 
melted  mixture  of  iron  and  carbon.     He  could  prepare  such 
a  mixture  with  his  electric  furnace,   he  thought,   and  so 
make  diamonds  like  those  of  the  diamond  mines.     So,  with 
an  electric  furnace  having  electrodes  as  large  as  a  man's 
wrist,  a  mixture  of  iron  and  charcoal  in  a  carbon  crucible, 
and  a  glass  tank  filled  with  water,  Moissan  set  out  to  change 
the  charcoal  to  diamonds.     At  a  temperature  of  more  than 
six  thousand  degrees  the  iron  and  charcoal  were  melted  to- 
gether.    For  a  time  of  from  three  to  six  minutes  the  mixture 
was  in  the  intense  heat.     Then  the  covering  of  the  furnace 
was  removed  and  the  crucible  with  the  melted  mixture 
dropped  into  the  tank  of  water.     With  some  fear  this  was 
done  for  the  first  time,  for  it  was  not  known  what  would 
happen  when   such  a  hot  object  was  dropped  into  cold 
water.     But  no  explosion  occurred,  only  a  violent  boiling 
of  the  water,  a  fierce  blazing  of  the  molten  mass,  and  then 
a  gradual  change  of  color  from  white  to  red  and  red  to 
black.     With  boiling  acids  and  other  chemicals  the  refuse 
was  removed,  and  the  fragments  that  remained  were  found 
to  be  diamonds,  small,  it  is  true,  so  small  that  they  could 
be  seen  only  with  the  aid  of  a  microscope,  but  giving  prom- 
ise of  greater  things  to  come.     Trie  outer  crust  of  iron  held 

206 


FIG.     105 MANUFACTURING    DIAMONDS FIRST    OPERATION 

Preparing  the  furnace.     Charcoal  and  iron  ore  placed  in  a  crucible  and 
subjected  to  enormous  heat  electrically. 


THE  STORY  OF  GREAT  INVENTIONS 

the  melted  charcoal  under  enormous  pressure  while  it 
slowly  cooled  and  formed  the  diamond  crystals.  The  proc- 
ess of  manufacturing  diamonds  is  illustrated  in  Figs.  105, 
106,  and  107. 

The  electric  furnace  has  made  possible  the  preparation 
of  substances  unknown  before,  and  the  production  in  large 
quantities  at  low  cost  of  substances  that  before  were  too 
costly  for  general  use.  One  of  the  best  known  of  these 
substances  is  aluminum.  With  the  discovery  of  the  electric- 
furnace  method  of  extracting  aluminum  from  its  ores,  the 
price  of  aluminum  fell  from  one  hundred  and  twenty-four 
dollars  per  pound  to  twelve  cents  per  pound. 

Among  the  many  uses  of  the  electric  furnace  we  may 
mention  the  preparation  of  calcium  carbide,  which  is  used 
in  producing  the  acetylene  light;  carborundum,  a  sub- 
stance almost  as  hard  as  diamond;  and  phosphorus,  which 
is  used  in  making  the  phosphorus  match.  It  is  used  also 
to  some  extent  in  the  manufacture  of  glass,  and,  in  some 
cases,  for  extracting  iron  from  its  ores. 

The  Wireless  Telegraph 

A  ship  in  a  fog  is  struck  by  another  ship.  The  water 
rushes  in,  puts  out  the  fires  in  the  boilers,  the  engines  stop, 
the  ship  is  helpless  in  mid-ocean  in  the  darkness  of  the  night. 
But  the  snapping  of  an  electric  spark  is  heard  in  one  of  the 
cabins.  Soon  another  vessel  steams  alongside.  The  life- 
boats are  lowered  and  every  person  is  saved.  The  call  for 
help  had  gone  out  over  the  sea  in  every  direction  for  two 
hundred  miles.  Another  ship  had  caught  the  signal  and 

208 


FIG.    I06—  MANUFACTURING    DIAMONDS SECOND    OPERATION 

The  furnace  at  work. 


THE  STORY  OF  GREAT  INVENTIONS 

hastened  to  the  rescue,  and  the  world  realized  that  the 
wireless  telegraph  had  robbed  the  sea  of  its  terrors. 

Without  the  curious  combination  of  magnets,  wires,  and 
batteries  on  the  first  ship  no  signal  could  have  been  sent, 
and  without  such  a  combination  on  the  second  ship  the 
signal  would  have  passed  unheeded.  How  was  this  com- 
bination discovered,  and  how  does  it  work? 

Faraday,  as  we  have  seen,  discovered  the  principle  of  the 
induction-coil.  With  the  induction-coil  a  powerful  electric 
spark  can  be  produced.  The  friction  electrical  machine  was 
known  long  before  the  time  of  Faraday.  Franklin  proved 
that  a  stroke  of  lightning  is  like  a  spark  from  an  electrical 
machine,  only  more  powerful.  These  great  discoverers  did 
not  know,  however,  that  an  electric  spark  sends  out  some- 
thing like  light  which  travels  in  all  directions.  They  did 
not  know  it,  because  they  had  no  eyes  to  see  this  strange 
light. 

I  will  tell  you  a  fable  to  make  the  meaning  clear.  There 
once  lived  a  race  of  blind  men.  Not  one  of  them  could  see. 
They  built  houses  and  cities,  railroads  and  steamships, 
but  they  did  everything  by  touch  and  sound.  When  they 
met  they  touched  each  other  and  spoke,  and  each  man 
knew  his  friend  by  the  sound  of  his  voice.  One  day  a  wise 
man  among  them  said  he  believed  there  was  something 
besides  the  sound  of  the  voice  with  which  they  could  make 
signals  to  each  other.  Another  wise  man  thought  upon 
this  matter  for  some  time  and  brought  forth  a  proof  that 
there  is  something  called  light,  though  no  man  could  see  it. 
Another,  wiser  and  more  practical,  invented  an  eye  which 
any  man  could  carry  about  with  him  and  see  the  light 

210 


FIG,     107 MANUFACTURING    DIAMONDS THIRD    OPERATION 

Plunging  the  crucible  into  cold  water.     Observe  the  white-hot  carbon 
just  removed  from  the  furnace. 


THE  STORY  OF  GREAT  INVENTIONS 

when  he  turned  it  in  the  direction  from  which  the  light 
was  coming.  Thereafter  each  man  carried  a  light  that 
flashed  like  the  flashing  of  a  firefly.  Each  man  also  carried 
an  eye,  and  each  could  see  his  friend  as  well  as  hear  the 
sound  of  his  voice. 

The  fable  is  true.  The  light  which  no  man  had  seen  we 
now  call  electric  waves.  The  eye  with  which  any  one  can 
perceive  this  light  is  the  receiving  instrument  of  the  wire- 
less telegraph.  The  strange  light  flashed  out  whenever  an 
electric  spark  passed  from  an  electrical  machine,  a  Ley  den 
jar,  an  induction-coil,  or  as  lightning  in  the  clouds,  but  for 
hundreds  of  years  this  light  was  unseen.  The  human  eye 
could  not  see  it,  and  no  artificial  eye  that  would  catch  elec- 
tric waves  had  been  invented.  A  man  in  England,  James 
Clerk-Maxwell,  first  proved  that  there  is  such  a  light.  Hein- 
rich  Hertz,  a  German,  first  made  an  eye  that  would  catch 
the  waves  from  the  electric  spark,  and  the  man  who  first 
perfected  an  eye  with  which  one  could  catch  the  electric 
waves  at  a  great  distance  and  improved  the  instruments 
for  sending  out  such  waves  was  Marconi. 

The  fable  is  true,  for  electric  waves  are  like  the  light  from 
the  sun.  They  go  through  space  in  all  directions  as  light 
does.  They  will  not  merely  go  through  air,  but  through 
what  we  call  empty  space,  or  a  vacuum,  as  light  will.  If  we 
think  of  waves  somewhat  like  water  waves,  but  not  exactly 
like  them,  rushing  through  space,  we  have  about  as  good  a 
picture  of  electric  waves  as  we  can  well  form  in  our  minds. 
As  the  light  of  a  lamp  goes  out  in  all  directions,  so  do  the 
electric  waves  go  out  in  all  directions  from  the  place  where 
the  electric  spark  passes.  Since  these  waves  go  through 

212 


THE   TWENTIETH-CENTURY   OUTLOOK 

what  we  call  empty  space,  we  must  think  of  something  in 
that  space  and  that  it  is  not  really  empty.  Examine  an  in- 
candescent electric  lamp.  The  bulb  was  full  of  air  when 
the  carbon  thread  was  placed  in  it.  The  air  was  then 
pumped  out  until  only  about  a  millionth  part  remained. 
The  bulb  was  then  sealed  at  the  tip  and  made  air-tight. 
We  say  the  space  inside  is  a  vacuum.  If  the  bulb  is  broken 
there  is  a  loud  report  as  the  air  rushes  in.  Is  the  bulb  really 
empty  after  the  air  is  pumped  out  ?  Is  anything  left  in  the 
bulb  around  the  carbon  thread?  Turn  on  the  electric  cur- 
rent and  the  carbon  thread  becomes  white  hot.  The  light 
from  the  white-hot  carbon  thread  goes  out  through  the 
vacuum.  There  is  nothing  in  the  vacuum  that  we  can  see 
or  feel  or  handle,  but  something  must  be  there  to  carry  the 
light  from  the  carbon  thread.  The  light  of  the  sun  comes 
to  the  earth  through  ninety-three  million  miles  of  space. 
Is  there  anything  between  the  earth  and  the  sun  through 
which  this  light  can  pass?  Light,  we  know,  is  made  up  of 
waves,  and  we  cannot  think  of  waves  going  through  empty 
space.  There  must  be  something  between  the  sun  and  the 
earth.  That  something  through  which  the  light  of  the  sun 
comes  to  the  earth  we  call  the  ether.  It  is  the  ether  that 
carries  the  light  across  the  vacuum  in  the  light  bulb  as  well 
as  from  the  sun  to  the  earth.  Electric  waves  used  in  wire- 
less telegraphy  go  through  this  same  ether.  The  light  of 
the  sun  is  made  up  of  the  same  kind  of  waves,  and  we  do 
not  think  it  strange  because  it  is  so  common.  It  is  true 
we  do  not  see  light  waves,  but  they  affect  our  eyes  so  that 
by  means  of  them  we  can  see  objects  and  perceive  the  flash- 
ing of  a  light.  So  with  the  wireless  receiving  instrument  we 

213 


THE  STORY  OF  GREAT  INVENTIONS 

do  not  see  the  electric  waves,  but  we  perceive  the  flashing 
of  the  strange  light.  Electric  waves  and  light  travel  with 
the  same  speed — 186,000  miles  in  a  second.  A  wireless 
message  will  go  around  the  earth  in  about  one-seventh  of 
a  second. 

Electric  waves  will  go  through  a  brick  wall  as  readily  as 
sunlight  will  go  through  a  glass  window,  but  that  is  not  so 
strange  as  it  may  seem.  Red  light  will  not  go  through  blue 
glass.  Blue  glass  holds  back  the  red  light,  but  lets  the 
blue  light  go  through.  So  the  brick  wall  holds  back  com- 
mon light,  but  allows  the  light  which  we  call  electric  waves 
to  go  through. 

Some  waves  on  water  are  longer  than  others.  So  electric 
waves  are  longer  than  light  waves.  That  is  the  only  differ- 
ence between  them.  In  fact,  the  light  of  the  sun  is  made 
up  of  very  short  electric  waves.  These  short  waves  affect 
our  eyes,  but  the  longer  electric  waves  do  not.  We  are  daily 
receiving  the  wireless-telegraph  waves  from  the  sun,  which 
we  call  light.  Electric  waves  used  in  wireless  telegraphy 
vary  from  about  six  hundred  feet  to  two  miles  in  length, 
while  the  longest  light  waves  that  affect  our  eyes  are  only 
one  thirty-three-thousandth  of  an  inch  in  length. 

The  sensitive  part  of  the  Marconi  receiving  apparatus  is 
the  coherer.  The  first  coherer  was  made  in  1890  by  Prof. 
Edward  Branly,  of  the  Catholic  University  of  Paris.  Very 
fine  metal  filings  were  enclosed  in  a  tube  of  ebonite  and 
connected  in  a  circuit  with  a  battery  and  a  galvanometer. 
The  filings  have  so  high  a  resistance  that  no  current  flows. 
The  waves  from  an  electric  spark,  however,  affect  the  filings 
so  that  they  allow  the  current  to  flow.  The  electric  waves 

214 


THE   TWENTIETH-CENTURY   OUTLOOK 

are  said  to  cause  the  filings  to  cohere — that  is,  to  cling  to- 
gether more  closely.  It  is  a  peculiar  form  of  electric  weld- 
ing. Branly  discovered  that  a  slight  tapping  of  the  tube 
loosens  the  filings  and  stops  the  flow  of  the  current. 

All  that  was  needed  for  wireless  telegraphy  was  at  hand. 
Men  knew  how  to  produce  electric  waves  of  any  desired 
length.  They  knew  how  they  would  act.  A  sensitive  re- 
ceiver had  been  discovered.  There  was  needed  the  prac- 
tical man  who  should  combine  the  parts,  improve  details, 
and  apply  the  wireless  telegraph  to  actual  use.  This  was 
the  work  of  Guglielmo  Marconi.  In  1894,  at  the  age  of 
twenty,  Marconi  began  his  experiments  on  his  father's 
estate,  the  Villa  Grifone,  Bologna,  Italy.  Fig.  108  is  from  a 
photograph  of  Marconi  and  his  wireless  sending  and  receiv- 
ing instruments. 


FIG.     I08 MARCONI     AND      HIS     WIRELESS-TELEGRAPH     SENDING     AND 

RECEIVING    INSTRUMENTS 

215 


THE  STORY  OF  GREAT  INVENTIONS 

To  Marconi,  telegraphing  through  space  without  wires 
appears  no  more  wonderful  than  telegraphing  with  wires. 
In  the  wire  telegraph  electric  waves,  which  we  then  call  an 
electric  current,  follow  a  wire  somewhat  as  the  sound  of  the 
voice  goes  through  a  speaking-tube.  -  In  the  wireless  telegraph 
the  electric  waves  go  out  through  space  without  any  wire 
to  guide  them.  The  light  and  heat  waves  of  the  sun  travei 
to  us  through  millions  of  miles  of  space  without  requiring  any 
conducting  wire.  That  electric  waves  should  go  though 
space  in  the  same  way  that  light  does  is  no  more  wonderful 
than  that  the  waves  should  follow  all  the  turns  of  a  wire. 

The  sending  instrument  used  by  Marconi  includes  an  in- 
duction-coil, one  side  of  the  spark-gap  being  connected  to 
the  earth  and  the  other  to  a  vertical  wire  (Fig.  109).  There 
must  be  a  battery  of  Leyden  jars  in  the  circuit  of  the  sec- 
ondary coil.  The  induction-coil  may  be  operated  by  a 
storage  battery  or  dynamo.  The  vertical  wire,  or  antenna, 
is  to  the  sending  instrument  what  the  sounding-board  is  to 
a  violin.  It  is  needed  to  increase  the  strength  of  the  waves. 
In  the  wireless  telegraph  some  wires  must  be  used.  It 
is  called  wireless  because  the  stations  are  not  connected 
by  wires.  The  antenna  for  long-distance  work  consists  of 
a  network  of  overhead  wires.  When  the  key  is  pressed  a 
rapid  succession  of  sparks  passes  across  the  spark-gap.  The 
antenna,  or  overhead  wire,  is  thus  made  to  send  out  electric 
waves.  By  pressing  the  key  for  a  longer  or  shorter  time,  a 
longer  or  shorter  series  of  waves  may  be  produced  and  a 
correspondingly  longer  or  shorter  effect  on  the  receiver.  In 
this  manner  the  dots  and  dashes  of  the  Morse  alphabet  may 
be  transmitted. 

216 


THE   TWENTIETH-CENTURY   OUTLOOK 


O  0 


Jn  due t ion -c  oil 


Earth 


FIG.    lOQ DIAGRAM    OF    WIRELESS-TELEGRAPH    SENDING    APPARATUS 

At  the  receiving  station  there  are  two  circuits.  One  in- 
cludes a  coherer,  a  local  battery,  and  a  telegraph  relay  (Fig. 
no).  The  other  circuit,  which  is  opened  and  closed  by  the 
relay,  includes  a  recording  instrument  and  a  tapper.  One 
end  of  the  coherer  is  connected  to  the  earth  and  the  other 
to  a  vertical  wire  like  that  used  for  the  transmitter.  The 

217 


THE  STORY  OF  GREAT  INVENTIONS 


electric  waves  weld  the  filings  in  the  coherer,  and  this  closes 
the  first  circuit.  The  relay  then  closes  the  second  circuit, 
the  recording  instrument  records  a  dot  or  a  dash,  and  the 
tapper  strikes  the  coherer  and  breaks  the  filings  apart  ready 
for  another  stream  of  electric  waves. 


Coherer 


Battery 


FIG.    110 DIAGRAM    OF    MARCONI    WIRELESS-TELEGRAPH    RECEIVING 

APPARATUS 

The  second  circuit  described  in  the  text  is  not  shown  here.  The  relay 
and  the  second  circuit  would  take  the  place  of  the  electric  bell.  In  the 
circuit  as  shown  here  the  electric  waves  would  cause  the  coherer  to  close 
the  circuit  and  ring  the  bell. 

218 


THE   TWENTIETH-CENTURY   OUTLOOK 

With  this  arrangement  it  was  possible  to  work  only  two 
stations  at  one  time.  Though  stations  were  to  be  estab- 
lished in  all  the  cities  of  Great  Britain,  only  one  message 
could  be  sent  at  one  time,  and  all  stations  but  one  must 
keep  silence,  because  a  second  series  of  waves  would  mingle 
with  the  first  and  confusion  would  result. 

Marconi's  next  effort  was  :o  make  it  possible  to  send  any 
number  of  messages  at  one  time.  This  led  to  his  system  of 
tuning  the  sending  and  receiving  instruments.  With  this 
system  the  receiving  instrument  will  take  a  message  only 
from  a  sending  instrument  with  which  it  is  in  tune.  It  is 
possible,  therefore,  for  any  number  of  wireless  -  telegraph 
stations  to  operate  at  the  same  time,  the  waves  crossing 
one  another  in  all  directions  without  interfering,  each 
receiver  responding  to  the  waves  intended  for  it.  An 
ocean  steamer  can,  with  the  tuned  system,  send  one  mes- 
sage and  receive  another  from  a  different  station  at  the 
same  time. 

Marconi's  ambition  was  to  send  a  wireless  message  across 
the  Atlantic.  Quietly  he  made  his  preparation,  building  at 
Poldhu,  Cornwall,  England,  a  more  powerful  transmitter 
than  had  yet  been  used.  At  noon  on  the  i2th  of  December, 
1901,  he  sat  in  a  room  of  the  old  barracks  on  Signal  Hill, 
near  St.  Johns,  Newfoundland,  waiting  for  a  signal  from 
England.  His  assistants  at  the  Poldhu  station  were  to 
telegraph  across  the  ocean  the  letter  ' '  S  "  at  certain  times 
each  day.  On  the  table  was  the  receiving  apparatus,  made 
very  sensitive,  and  including  a  telephone  receiver.  A  wire 
led  out  of  the  window  to  a  huge  kite,  which  the  furious  wind 
held  four  hundred  feet  above  him.  One  kite  and  a  balloon 

219 


THE  STORY  OF  GREAT  INVENTIONS 


used  for  supporting  the  antenna  had  been  carried  out  to 
sea.  He  held  the  telephone  receiver  to  his  ear  for  some 
time.  The  critical  time  had  come  for  which  he  had  worked 
for  years,  for  which  his  three  hundred  patents  had  prepared 
the  way,  and  for  which  his  company  had  erected  the  costly 
power  station  at  Poldhu.  Calmly  he  listened,  his  face 
showing  no  sign  of  emotion.  Suddenly  there  sounded  the 
sharp  click  of  the  tapper  as  it  struck  the  coherer.  After  a 
short  time  Marconi  handed  the  telephone  receiver  to  his 
assistant.  "See  if  you  can  hear  anything,"  he  said.  A 
moment  later,  faintly  and  yet  distinctly,  came  the  three 
little  clicks,  the  dots  of  the  letter  "S"  tapped  out 
an  instant  before  in  England.  Marconi's  victory  was 
won. 

A  flying-machine  can  de  equipped  with  a  wireless-tele- 
graph outfit,  so  that  a  man  can  telegraph  while  flying 
through  the  air.  Two  men  are  needed,  one  to  operate  the 
flying-machine,  the  other  to  send  the  telegraphic  messages. 
This  has  been  done  with  the  Wright  machine  and  with  some 
dirigible  balloons.  Of  course,  the  wireless  instruments  on 
the  flying-machine  cannot  be  connected  to  the  ground.  In- 
stead of  the  ground  connection  there  is  a  second  antenna,— 
one  antenna  on  each  side  of  the  spark-gap.  While  in  the 
ordinary  wireless  instruments  the  discharge  surges  back 
and  forth  between  the  antenna  and  the  earth,  in  the  flying- 
machine  wireless  the  discharge  surges  back  and  forth  be- 
tween the  two  antennae.  In  the  Wright  machine,  when 
equipped  for  wireless  telegraphy,  the  two  antennae  are 
placed  one  under  the  upper  plane,  the  other  under  the  lower 
plane  of  the  flying-machine. 


THE   TWENTIETH-CENTURY   OUTLOOK 

More  power  is  required  for  the  wireless  than  for  the  wire 
telegraph.  In  the  wire  telegraph  about  one-hundredth 
horse-power  is  required  to  send  a  message  one  hundred  and 
twenty  miles.  To  send  a  message  the  same  distance  with 
the  wireless  requires  about  ten  horse-power,  or  a  thousand 
times  as  much  as  with  the  wire  telegraph.  This  is  because 
in  the  wireless  telegraph  the  waves  go  out  in  all  directions, 
and  much  of  the  power  is  wasted.  In  the  wire  telegraph 
the  electric  waves  are  directed  along  the  wire  and  very  little 
of  the  power  is  wasted.  For  the  same  reason  a  person's 
voice  can  be  heard  a  long  distance  through  a  speaking-tube. 
The  speaking-tube  guides  the  sound  and  prevents  it  from 
scattering  somewhat  as  the  wire  guides  the  electric  waves. 

The  overhead  wires  of  a  wireless-telegraph  station  send 
out  a  "dark"  light  while  a  message  is  being  sent.  (See 
frontispiece.)  Standing  near  the  station  on  a  dark  night 
one  can  see  nothing,  but  can  hear  only  the  terrific  snapping 
of  the  electric  discharge.  The  camera,  however,  shows  that 
light  goes  out  from  the  wires.  It  is  light  of  shorter  waves 
than  any  that  the  eye  can  perceive,  but  the  sensitive  film 
of  the  photographic  plate  makes  it  known  to  us. 

The  Wireless  Telephone 

In  sending  a  message  by  the  wire  telegraph  the  current 
flows  over  the  line  wire  when  the  key  is  pressed.  When  the 
key  is  released  the  current  stops.  The  circuit  is  made  and 
broken  for  every  dot  or  dash.  This  we  may  call  an  inter- 
rupted current.  Now  we  have  seen  that  the  attempt  to 
invent  a  wire  telephone  using  an  interrupted  current  failed. 

221 


THE  STORY  OF  GREAT  INVENTIONS 

While  one  is  talking  over  the  wire  telephone  a  current 
(alternating)  must  be  flowing  over  the  line  wire.  The  sound 
of  the  voice  does  not  make  and  break  the  circuit,  but 
changes  the  strength  of  the  current.  This  alternating  cur- 
rent is  wonderfully  sensitive.  It  can  vary  in  the  rate  at 
which  it  alternates  or  the  number  of  alternations  per  second 
to  correspond  to  sound  of  every  pitch.  It  varies  in  strength 
to  correspond  to  all  the  variations  in  the  voice,  and  repro- 
duces in  the  receiver  not  merely  the  words  that  are  spoken 
but  the  quality  of  the  voice,  so  that  the  voice  of  a  friend 
can  be  recognized  by  telephone  almost  as  well  as  if  talking 
face  to  face. 

The  same  things  are  true  of  the  wireless  telegraph  and 
telephone.  Instead  of  an  electric  current,  let  us  say  ''a 
stream  of  electric  waves."  Then  we  may  say  of  the  wire- 
less everything  that  we  have  said  of  the  wire  telegraph  and 
telephone.  In  sending  a  message  by  wireless  telegraph  the 
stream  of  electric  waves  flows  when  the  key  is  pressed  and 
stops  when  the  key  is  released.  We  have  an  interrupted 
stream  of  felectric  waves.  But  an  interrupted  stream  of 
waves  cannot  be  used  for  a  wireless  telephone  any  more 
than  an  interrupted  current  can  be  used  for  a  wire-telephone. 
There  must  be  a  constantly  flowing  stream  of  electric  waves, 
and  these  waves  must  be  changed  in  strength  and  form  by 
the  sound  of  the  voice.  Fig.  in  shows  a  wireless-telephone 
receiver  in  which  light  is  used  to  carry  the  message.  The  light 
acts  on  the  receiver  in  such  a  way  as  to  reproduce  the  sound. 

In  the  wireless-telegraph  receiver  the  interrupted  stream 
of  electric  waves  makes  and  breaks  the  circuit  of  an  electric 
battery.  The  wireless-telephone  receiver  must  not  make 

222 


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THE  STORY  OF  GREAT  INVENTIONS 


and  break  a  circuit,  but  it  must  be  sensitive  to  all  the 
changes  in  the  electric  waves.  One  such  receiver  is  the 
audion,  which  we  shall  now  describe. 

The  audion  was  invented  by  Dr.  Lee  de  Forest.  De 
Forest  had  taken  the  degree  of  Doctor  of  Philosophy  at 
Yale  University,  having  written  his  thesis  for  that  degree 


Telephone 
receiver 


FIG.     112 A    GAS    FLAME    IS    SENSITIVE    TO    ELECTRIC    WAVES 

on  the  subject  of  electric  waves.  He  then  entered  the  em- 
ploy of  the  Western  Electric  Company  in  Chicago,  and  while 
in  this  position  worked  at  night  in  his  room  on  experiments 
with  electric  waves. 

Here  he  found  that  a  gas  flame  is  sensitive  to  electric 
waves  (Fig.  112).     If  a  gas  flame  is  made  part  of  the  circuit 

224 


THE   TWENTIETH-CENTURY   OUTLOOK 

of  an  electric  battery,  which  includes  also  an  induction-coil 
connected  to  a  telephone  receiver,  then  when  a  stream  of 
electric  waves  comes  along  there  is  a  click  in  the  receiver. 
The  waves  change  the  resistance  of  the  flame,  and  so  change 
the  strength  of  the  current.  The  flame  is  a  simple  audion. 
It  is  the  heated  gas  in  the  flame  that  responds  to  the  electric 
waves. 

If  instead  of  a  gas  flame  an  incandescent-light  bulb  is 
used  having  a  metal  filament,  and  on  either  side  of  the  fila- 
ment a  small  strip  of  platinum,  a  more  sensitive  receiver  is 
obtained.  This  is  the  audion,  which  is  the  distinguishing 
feature  of  the  De  Forest  wireless  telegraph  and  wireless 
telephone.  The  metal  filament  is  made  white  hot  by  the 
current  from  a  storage  battery.  The  vacuum  in  the  bulb  is 
about  the  same  as  that  of  the  ordinary  incandescent  electric 
light.  A  very  small  quantity  of  gas  is  therefore  left  in  the 
bulb.  The  electrified  particles  of  gas  respond  more  freely 
to  electric  waves  in  this  bulb  than  in  the  gas  flame. 

The  De  Forest  wireless  telephone  was  adopted  for  use 
in  the  United  States  Navy  shortly  before  the  cruise  around 
the  world  in  1908.  Every  ship  in  the  navy  was  equipped 
with  the  wireless  telephone,  enabling  the  Admiral  to  talk 
with  the  officers  of  any  vessel  up  to  a  distance  of  thirty-five 
miles.  The  wireless  telephone  in  use  on  a  battle-ship  is 
shown  in  Fig.  113. 

Wonders  of  the  Alternating  Current 

Before  the  days  of  the  electric  current,  men  used  the 
power  of  falling  water,  The  mill  or  factory  using  the  water- 

225 


THE  STORY  OF  GREAT  INVENTIO NS_ 

power  was  placed  beside  the  fall.  The  water  turned  a  great 
wheel,  to  which  was  connected  the  machinery  of  the  mill. 
It  was  not  until  the  invention  of  the  dynamo  and  motor 
that  water-power  could  be  used  at  a  great  distance.  If  a 


FIG.    113 CAPTAIN   INGERSOLL  ON   BOARD   THE   U.   S.   BATTLE-SHIP 

"CONNECTICUT"  USING  THE  WIRELESS  TELEPHONE 

hundred  years  ago  a  man  had  said  that  the  time  would  come 
when  a  waterfall  could  turn  the  wheels  of  a  mill  a  hundred 
miles  away  he  would  have  been  laughed  at.  Yet  this  very 

226 


THE   TWENTIETH-CENTURY   OUTLOOK 

thing  has  come  to  pass.  Indeed,  one  waterfall  may  turn 
the  wheels  of  many  factories,  run  street -cars,  and  light 
cities  up  to  a  distance  of  a  hundred  miles  and  even  more. 
The  power  of  the  falling  water  goes  out  over  slender  copper 
wires  from  a  great  dynamo  near  the  fall  to  the  motors  in 
the  factories  and  street-cars. 

The  falling  water  of  Niagara  has  about  five  million  horse- 
power. About  the  hundredth  part  of  this  power  is  now 
being  used.  The  water,  falling  in  a  wheel-pit  141  feet  deep, 
turns  a  great  dynamo  weighing  87,000  pounds  with  a  speed 
of  250  turns  per  minute.  A  number  of  such  dynamos  are 
used  supplying  an  alternating  current  at  a  pressure  of 
22,000  volts,  the  current  alternating  or  changing  direction 
twenty-five  times  per  second.  Such  a  pressure  is  too  high 
for  the  motors  and  electric  lights,  but  the  current  is  carried 
at  high  pressure  to  the  place  where  it  is  to  be  used  and 
there  transformed  to  a  current  of  low  pressure.  In  carry- 
ing a  current  over  a  long  line,  there  is  less  loss  if  the  cur- 
rent is  carried  at  high  pressure.  With  an  alternating 
current  this  can  be  done  and  the  current  changed  by 
means  of  a  transformer  to  a  current  of  low  pressure. 

A  transformer  is  simply  two  coils  of  wire  wound  on  an 
iron  core.  The  simplest  transformer  is  the  form  used  by 
Faraday  when  he  discovered  electromagnetic  induction.  If 
instead  of  making  and  breaking  a  circuit  that  flows  only  in 
one  direction  as  Faraday  did,  we  cause  an  alternating  cur- 
rent to  flow  through  one  of  the  coils,  which  we  may  call  the 
primary,  each  time  the  current  changes  direction  in  the 
primary  the  magnetic  field  is  reversed — that  is,  the  end  of 
the  coil  which  was  the  north  pole  becomes  the  south  pole. 

227 


THE  STORY  OF  GREAT  INVENTIONS 


This  rapidly  changing  magnetic  field  induces  a  current  in 
the  secondary  coil.  Each  time  the  magnetic  field  of  the 
primary  coil  is  reversed  the  current  in  the  secondary  changes 
direction.  Thus  an  alternating  current  in  the  primary  in- 
duces an  alternating  current  in  the  secondary.  One  of  these 
coils  is  of  fine  wire,  which  is  wound  a  great  many  times 
around  the  iron.  The  other  is  of  coarser  wire  wound  only 
a  few  times  around  the  iron.  Suppose  the  current  is  to  be 
changed  from  high  pressure  to  low  pressure.  Then  the  high- 
pressure  current  from  the  line  is  made  to  flow  through  the 
coil  of  many  turns,  and  a  current  of  low  pressure  is  given  out 
from  the  coil  of  few  turns.  By  changing  the  number  of 
turns  of  wire  in  the  coils  we  can  make  the  pressure  whatever 
we  please.  If  the  pressure  or  voltage  of  the  secondary  coil 
is  less  than  that  of  the  primary,  we  have  a  " step-down" 
transformer.  On  the  other  hand,  if  we  send  the  current 
from  the  line  wire  through  the  coil  of  few  turns,  then  we 
get  a  higher  voltage  from  the  secondary  coil  than  that  of  the 
line  wire,  and  we  have  a  "step-up"  transformer.  The 
Niagara  current  is  "stepped  down"  from  22,000  volts  to 
220  volts  for  use  in  motors. 

An  electric  lamp  may  be  lighted  though  not  connected  to 
any  battery  or  dynamo,  but  connected  only  to  a  coil  of 
wire  (Fig.  114).  More  than  this,  the  coil  may  be  insulated 
so  that  no  current  can  enter  it  from  any  other  coil  or  wire, 
and  yet  the  lamp  can  be  lighted.  This  can  be  done  only  by 
means  of  an  alternating  current.  If  the  coil  to  which  the 
lamp  is  connected  is  held  in  the  magnetic  field  of  an  alter- 
nating current,  then  another  alternating  current  is  induced 
in  the  coil,  and  this  second  current  flows  through  the  lamp. 

228 


THE    TWENTIETH-CENTURY   OUTLOOK 


- 


FIG.      114 INCANDESCENT     ELECTRIC     LAMP     LIGHTED     THOUGH     NOT     CON- 
NECTED   TO    ANY    BATTERY    OR    DYNAMO 


We  have  already  learned  that  a  changing  magnetic  field  in- 
duces a  current  in  a  coil.  Now  the  coil  through  which  an 
alternating  current  is  flowing  has  a  changing  magnetic  field 
all  around  it,  and  if  the  lamp-coil  is  brought  into  this 
changing  magnetic  field  an  alternating  current  will  flow 
through  the  coil  and  the  lamp.  The  insulation  on  the 
lamp-coil  does  not  prevent  the  magnetic  field  from  acting, 

229 


THE  STORY  OF  GREAT  INVENTIONS 

though  it  does  prevent  a  current  from  entering  the  coil. 
The  current  is  induced  in  the  coil  itself,  and  does  not  enter 
it  from  any  outside  source. 

The  transformer  works  in  the  same  way,  the  only  differ- 
ence being  that  in  the  transformer  the  two  coils  are  on  the 


FIG.    115— AN    ELECTRIC    DISCHARGE    AT    A    PRESSURE    OF    I2,OOO,OOO    VOLTS, 
A  CURRENT  OF  8oO  AMPERES  IN  THE   SECONDARY  COIL 


same  iron  core.  But  in  the  transformer  the  two  coils  are 
insulated  so  that  no  current  can  flow  from  one  coil  to  the 
other.  When  an  alternating  current  and  transformers  are 
used,  .the  current  that  lights  the  lamps  in  the  houses  or  on 
the  streets  is  not  the  current  from  the  dynamo.  It  is  a  new 

230 


THE   TWENTIETH-CENTURY   OUTLOOK 


current  induced  in  the  secondary  coil  of  the  transformer  by 
the  magnetic  field  of  the  primary  coil. 

A  peculiar  transformer  which  produces  an  alternating 
current  that  changes  direction  millions  of  times  in  a  second 
has  been  made  by  Nikola  Tesla.  This  current  will  do  many 
wonderful  things  which  no  ordinary  current  will  do.  It 
will  light  a  room  or  run  a  motor  without  connecting 
wires.  It  has  produced  an  electric  discharge  sixty -five 
feet  in  length  (Figs.  115  and  116).  Though  this  current 
is  caused  to  flow  by  a  pressure  of  millions  of  volts,  it  may 
be  taken  with  safety  through  the  human  body.  Strange  as 
it  may  seem,  the  safety  of  this  current  is  due  to  the  high 


FIG.     Il6. \N    ELECTRIC    DISCHARGE    SIXTY-FIVE    FEET    IN    LENGTH 

231 


THE  STORY  OF  GREAT  INVENTIONS 

pressure  and  the  rapidity  with  which  it  changes  direction. 
While  the  current  used  at  Sing  Sing  in  executing  criminals 
has  a  pressure  of  about  twenty-five  hundred  volts,  a  current 
having  a  pressure  of  a  million  volts  and  alternating  hundreds 
of  thousands  or  millions  of  times  per  second  is  harmless. 
With  such  a  current  the  human  body  may  become  a  "live 
wire,"  and  an  electric  lamp  to  be  lighted  held  in  one  hand 
while  the  other  hand  grasps  the  wire  from  the  transformer. 

X-Rays  and  Radium 

A  strange  light  which  passes  through  the  human  body  as 
readily  as  sunlight  through  a  window  was  discovered  by 
Prof.  Wilhelm  Konrad  Roentgen,  of  the  University  of  Wiirz- 
burg.  This  light,  which  Professor  Roentgen  named  X-rays, 
is  given  out  when  an  electric  discharge  at  high  pressure 
passes  through  a  certain  kind  of  glass  tube  from  which  the  air 
has  been  pumped  out  until  there  is  a  nearly  perfect  vacuum. 

X-rays  were  discovered  by  accident.  Professor  Roentgen 
was  working  at  his  desk  with  one  of  the  glass  tubes  when 
he  was  called  to  lunch.  He  laid  the  tube  with  the  electric 
discharge  passing  through  it  on  a  book.  Returning  from 
lunch  he  took  a  photographic  plate-holder  which  was  under 
the  book  and  made  some  outdoor  exposures  with  his 
camera.  On  developing  the  plates  a  picture  of  a  key  ap- 
peared on  one  of  them.  He  was  greatly  puzzled  at  first, 
but  after  a  search  for  the  key  found  it  between  the  leaves 
of  the  book.  The  strange  light  from  the  electric  discharge 
in  the  glass  tube  had  passed  through  the  book  and  the  hard- 
rubber  slide  of  the  plate-holder  and  made  a  shadow-picture 

232 


FIG.    117 A    PHYSICIAN    EXAMINING    THE    BONES    OP    THE    ARM    BY    MEANS 

OP    X-RAYS 


THE  STORY  OF  GREAT  INVENTIONS 

of  the  key  on  the  photographic  plate.  He  tried  the  strange 
light  in  many  ways,  and  found  that  it  would  go  through 
many  objects.  It  would  even  go  through  the  human  body, 
so  that  shadow-pictures  of  the  bones  and  organs  of  the 
body  could  be  obtained.  In  Fig.  117  is  shown  a  physician 
using  X-rays.  Fig.  118  is  an  X-ray  photograph  of  the  eye. 


FIG.  Il8 X-RAY  PHOTOGRAPH  OF  THE  EYE 

The  eye  is  above  and  to  the  left  of  the  larger  black  circle.  The  smaller 
black  circle  is  a  shot  which  has  lodged  back  of  the  eye. 

Not  long  after  the  discovery  of  X-rays  it  was  discovered 
that  light  very  much  like  the  X-rays  is  given  out  by  certain 
minerals.  One  of  the  most  interesting  and  the  best  known 
of  these  is  radium.  Radium  gives  out  a  light  somewhat 
like  X-rays  that  will  go  through  copper  and  other  metals. 
It  does  many  other  strange  things.  It  gives  out  heat  as 

234 


THE   TWENTIETH-CENTURY   OUTLOOK 

well  as  light;  so  much  heat,  in  fact,  that  it  is  always  about 
five  degrees  warmer  than  the  air  around  it.  It  continues 
to  give  out  heat  at  such  a  rate  that  a  pound  of  radium  will 
melt  a  pound  of  ice  every  hour.  It  can  probably  keep  this 
up  for  at  least  a  thousand  years.  If  this,  heat  could  be 
used  in  running  an  engine,  a  hundred  pounds  of  radium 
would  run  a  one-horse-power  engine  without  stopping  for 
many  hundred  years.  The  power  of  Niagara  might  be  re- 
placed by  the  power  of  radium  if  an  engine  that  could  use 
this  power  were  invented.  Fig.  119  is  from  a  photograph 
made  with  radium. 


FIG.     119 PHOTOGRAPH    MADE    WITH    RADIUM 

A  purse  containing  a  coin.  The  strange  light  from  the  radium  goes 
through  the  purse  and  the  slide  of  the  plate-holder  and  makes  a  shadow- 
picture. 

235 


THE  STORY  OF  GREAT  INVENTIONS 

The  great  inventor  of  the  future  may  be  able  to  use  the 
heat  of  radium  or  some  new  power  now  unknown.  We 
have  seen  how,  through  the  toil  of  many  years  and  the 
labors  of  many  men,  the  great  inventions  of  our  age  have 
come  into  being.  It  may  be  that  we  are  now  witnessing 
other  great  inventions  in  the  making. 


APPENDIX 

BRIEF  NOTES  ON  IMPORTANT  INVENTIONS 

Aerial  Navigation 

air  balloon — Montgolfier  Brothers,  France,   1783. 

1     First  balloon  ascension — Rozier,  France.  1783. 

First  gas  balloon — Charles,  France,  1783. 

First  crossing  of  the  English  Channel  in  a  balloon — Blanchard,  1785. 

First  successful  dirigible  balloon — La  France,  Renard  and  Krebs, 
France,  1884. 

First  successful  motor-driven  aeroplane — Wright  Brothers,  United 
States;  date  of  patent,  1906. 

First  crossing  of  the  English  Channel  by  an  aeroplane — Bleriot,  1909. 

First  air-ship  in  regular  passenger  service — Count  Zeppelin,  Ger- 
many, 1910. 

Agriculture 

Plough  with  cast-iron  mold-board  '  and  iron  shares — James  Small, 
Scotland,  1784. 

Grain-threshing  machine — Andrew  Meikle,  England,   1788. 

McCormick  reaper,  first  practical  grain  -  harvesting  machine — 
Cyrus  H.  McCormick,  United  States,  1831. 

Self -raker  for  harvesters — McCormick,    1845. 

Inclined  platform  and  elevator  in  the  reaper,  to  enable  men  bind- 
ing the  grain  to  ride  with  the  machine — J.  S.  Marsh,  United 
States,  1858. 

Barbed-wire  fence  introduced — United  States,   1861. 

Self-binder,  first  automatic  grain-binding  device  for  the  reaper — 
Jacob  Behel,  United  States,  1864. 

Sulky  plough — B.  Slusser,  United  States,  1868. 

237 


THE  STORY  OF  GREAT  INVENTIONS 

Twine-binder  for  harvesters — M.  L.  Gorham,  United  States,  1873. 
Improved  self-binding  reaper — Lock  and  Wood,  United  States,  1873. 
Barbed-wire  machine — Glidden  and  Vaughn,  United  States,  1874. 
Rotary  disk  cultivator — Mallon,  United  States,  1878. 
Steam-plough — W.  Foy,  United  States,  1879. 

Combined  harvester  and  thresher — Matteson,  United  States,  1886. 
Automobile  mower — Deering  Harvester  Company,  United  States, 
1901. 

Automobile 

First  steam-automobile — Cugnot,  France,   1769. 

First  chain  transmission  of  power  in  an  automobile  —  Gurney, 
England,  1829. 

Application  of  gas-engine  to  road  vehicles,  beginning  of  the  modern 
motor-car — Gottlieb  Daimler  and  Carl  Benz  working  independ- 
ently, Germany,  1886.  Daimler's  invention  consisted  of  a 
two-cylinder  air-cooled  motor.  It  was  taken  up  in  1889  by 
Panhard  and  Levassor,  of  Paris,  who  began  immediately  the 
construction  of  the  motor-car.  This  was  the  beginning  of  the 
motor-car  industry. 

Bicycle 

First  bicycle— Branchard  and  Magurier,   France.    1779. 
Rear-driven  chain  safety  bicycle — George  W.  Marble,  United  States, 

1884. 
Bicycles  first  equipped  with  pneumatic  tires — 1890. 

Electrical  Inventions 

William  Gilbert,  England,  1540-1603,  called  "  the  father  of  magnetic 
philosophy,"  first  to  use  the  terms  "electric  force,"  "electric 
attraction,"  "magnetic  pole." 

First  electrical  machine,  a  machine  for  producing  electricity  by 
friction — Otto  von  Guericke,  Germany,  about  1681. 

Discovery  of  conductors  and  insulators — Stephen  Gray,  England, 
1696-1736. 

First  to  discover  that  electric  charges  are  of  two  kinds — Cisternay 
du  Fay,  France,  1698-1739;  Du  Fay  was  also  the  first  to  at- 
tempt an  explanation  of  electrical  action.  He  supposed  that 
electricity  consists  of  two  fluids  which  are  separated  by  friction, 

238 


APPENDIX 

and  which  neutralize  each  other  when  they  combine.     This 
theory  was  more  fully  set  forth  by  Robert  Symmer. 

Leyden  jar  —  Discovered  first  by  Von  Kleist  in  1745.  The  same 
discovery  was  made  and  the  Leyden  jar  brought  to  the  atten- 
tion of  the  public  in  1 746  by  Pieter  van  Musschenbroek  in  Holland. 

Lightning-rod — Benjamin  Franklin,  1732. 

Electroplating — Luigi  Brugnatelli,  Italy,   1805. 

Voltaic  arc,  a  powerful  arc  light  produced  with  a  battery  current — 
vSir  Humphry  Davy,  England,  1808. 

Storage  battery — Ritter,  Germany,  1803.  Platinum  wires  were 
dipped  in  water  and  a  battery  current  passed  through.  Hydro- 
gen collected  on  one  wire  and  oxygen  on  the  other.  If  the 
platinum  wires  were  disconnected  from  the  battery  and  con- 
nected with  each  other  by  a  conductor,  the  two  wires  acted 
like  the  plates  of  a  battery,  and  a  current  would  flow  for  a  short 
time  in  the  new  circuit. 

Electromagnetism  discovered — H.  C.  Oersted,  Denmark,  1819. 

Galvanometer,  a  coil  of  wire  around  a  magnetic  needle  for  measur- 
ing the  strength  of  an  electric  current — Schweigger,  Germany, 
1820. 

Motion  of  magnet  produced  by  an  electric  current — M.  Faraday, 
England,  1821. 

Thermo-electricity,  an  electric  current  produced  by  heating  the 
junction  of  two  unlike  metals — Discovered  by  Professor  See- 
beck,  England,  1821. 

Principles  of  electrodynamics,  motion  produced  by  an  electric  cur- 
rent— Ampere,  France.  Announced  in  1823. 

Law  of  electric  circuits,  Ohm's  law,  current  strength  equals  electro- 
motive force  divided  by  resistance  of  the  circuit — George  S. 
Ohm,  Germany.  Proven  by  experiment  in  1826 ;  mathematical 
proof  published  in  1827. 

Magnetr  -  Metric  induction,  induction  of  electric  currents  by  means 
01  a  magnetic  field — M.  Faraday,  England,  1831. 

F1jctric  telegraph — Prof.  S.  F.  B.  Morse,  United  States,  1832. 

First  telegram  sent  in  1844 — Morse. 

Constant  electric  battery — J.  P.  Daniell,  England,  1836. 

First  electric  motor-boat — Jacobi,  Russia,  1839. 

Induction-coil — Rhumkorff,   Germany,    1851. 

Duplex  telegraph,  first  practical  system — Stearns,  United  States, 
about   1855-1860. 
16  239 


THE  STORY  OF  GREAT  INVENTIONS 

Storage  battery,  lead  plates  in  sulphuric  acid — Gaston  Plante, 
France,  1859. 

Telephone,  make-and-break  system,  first  electrical  transmission  of 
speech — Philip  Reiss,  Germany,  1860. 

Atlantic  cable  laid — Cyrus  W.  Field,   1866. 

Dynamo,  armature  coil  rotates  in  the  field  of  an  electromagnet, 
armature  supplies  current  for  the  electromagnet  as  well  as 
for  the  external  circuit — William  Siemens,  Germany,  1866. 

Gramme  ring  armature  for  dynamo — Gramme,  France,   1868. 

Theory  that  light  consists  of  electromagnetic  waves — Clerk- Max- 
well, England,  1873. 

Quadruplex  telegraph,  sending  four  messages  over  one  wire  at  the 
same  time — Edison,  1873. 

Siphon  recorder  for  submarine  telegraph,  sensitive  to  very  feeble 
currents — Sir  William  Thomson,  England,  1874. 

Telephone,  varying  current,  first  practical  working  telephone — 
Alexander  Graham  Bell,  United  States,  1876. 

Electric  candle,  beginning  of  present  arc  light — Paul  Jablochkoff, 
Russia,  1876. 

Telephone  transmitter  of  variable  resistance — Emil  Berliner  and 
Edison  working  independently,  United  States,  1877.  Edison 
used  carbon  contacts,  Berliner  used  metal  contacts. 

Brush  system  of  arc  lighting — 1878. 

Incandescent  electric  lamp  with  carbon  filament — Edison,   1878. 

First  electric  locomotive — Siemens,  Germany,   1879. 

Blake  telephone  transmitter — Blake,    United   States,    1880. 

Storage  battery,  lead  grids  filled  with  active  material — Faure, 
France,  1881. 

Electric  welding — Elihu  Thompson,  United  States,   1886. 

Electric  waves  discovered  by  experiment — Heinrich  Hertz,  Ger- 
many, 1888. 

Coherer  for  receiving  electric  waves  —  Edward  Branly,  France, 
1890. 

X-rays — Discovered  by  Prof.  W.  C.  Roentgen,  Germany;  announced 
to  the  public  in  1895. 

Wireless  telegraphy — G.  Marconi,  Italy,  1896.  v 

Nernst  electric  light,  a  clay  capable  of  conducting  electricity  when 
heated  is  used;  it  becomes  incandescent  without  a  vacuum — 
Walter  Nernst,  Germany,  1897. 

Radium  discovered  by  Madame  Curie,  France,   1898. 

240 


APPENDIX 

Explosives 

Gunpowder — Inventor  and  date  unknown. 

Guncotton — Schonbein,  Germany,   1845. 

Nitroglycerine — Sobrero,    1847.  ..•*. 

Explosive  gelatine — A.  Nobel,  France,  1863. 

Dynamite — A  Nobel,  France,  1866. 

Smokeless  powder — Vielle,  France,   1866. 

Firearms  and  Ordnance 

Spirally  grooved  rifle  barrel — Koster,  England,  1620. 

Breech-loading  shot-gun — Thornton  and  Hall,  United  States,  1811. 

The  revolver;  a  device  "for  combining  a  number  of  long  barrels 
so  as  to  rotate  upon  a  spindle  by  the  act  of  cocking  the  ham- 
mer"— Samuel  Colt,  United  States,  1836. 

Breech  gun-lock,  interrupted  thread — Chambers,  United  States,  1849. 

Magazine  gun — Walter  Hunt,  United  States,  1849. 

Breech-loading  rifle — Maynard,  United  States,   1851. 

Iron-clad  floating  batteries  first  used  in  Crimean  War — 1855. 

Breech-loading  ordnance — Wright  and  Gould,  United  States,  1858. 

Revolving  turret  for  floating  batteries — Theodore  Timby,  United 
States,  1862. 

First  iron-clad  floating  battery  propelled  by  steam:  the  Monitor — 
John  Ericsson,  United  States,  1862. 

Gatling  gun — Dr.  R.  J.  Gatling,  United  States,  1862. 

Automatic  shell-ejector  for  revolver — W.  C.  Dodge,  United  States, 
1865. 

Torpedo — Whitehead,  United  States,   1866. 

Disappearing  gun-carriage — Moncrief,  England,  1868. 

Rebounding  gun-lock — L.  Hailer,  United  States,   1870. 

Magazine  rifle — Lee,  United  States,   1879. 

Hammerless  gun — Greener,  United  States,  1880. 

Gun  silencer,  to  be  attached  to  barrel  of  gun;  gun  can  be  fired 
without  noise — Maxim,  1909. 

Gas  Used  for  Light  and  Power 

Gas  first  used  for  illuminating  purposes — William  Murdoch,  England, 

1792. 

First  street  gas-lighting  in  England — F.  A,  Winsor,  1814. 

241 


THE  STORY  OF  GREAT  INVENTIONS 

Gas-meter — S.  Clegg,  England,  1815. 

Water-gas,  prepared  by  passing  steam  over  white-hot  anthracite 

coal — First  produced  in  England  in  1823. 
Illuminating  water-gas — Lowe,  United  States,   1875. 
Gas-engine,    4-cycle,    beginning  of   modern   gas-engine — Otto   and 

Langen,  Germany,  1877. 
Incandescent  gas-mantle — Carl  A.  von  Welsbach,  Austria,  1887. 

Iron  and  Steel 

Blast-furnace,  beginning  of  iron  industry — Belgium,   1340. 

Use  of  coke  in  blast  -  furnace  —  Abram  Darly,  England,  about 
1720. 

Puddling  iron — Henry  Cort,  England,   1783-84. 

Process  of  making  malleable-iron  castings — Lucas,  England,  1804. 

Hot-air  blast  for  iron  furnaces — J.  B.  Neilson,  Scotland,  1828. 

The  galvanizing  of  iron — Henry  Craufurd,  England,    1837. 

Process  of  making  steel,  blowing  air  through  molten  pig-iron  to 
burn  out  carbon,  then  adding  spiegel  iron;  first  production  of 
cheap  steel — Sir  Henry  Bessemer,  England,  1855. 

Regenerative  furnace,  a  gas-furnace  in  which  gas  and  air  are 
heated  before  being  introduced  into  the  furnace,  giving  an 
extremely  high  temperature  —  William  Siemens,  England, 
1856. 

Open-hearth  process  of  making  steel — Siemens-Martin,  England, 
1856. 

Nickel  steel,  much  stronger  than  ordinary  steel,  used  for  armor- 
plate — Schneider,  United  States,  1889. 

Mining 

Miners'  safety-lamp — Sir  Humphry  Davy,  England,  1815. 

Compressed-air  rock-drill — C.   Burleigh,   United  States,    1866. 

Diamond  rock-drill,  a  tube  of  cast-steel  with  a  number  of  black 
diamonds  set  at  one  end.  The  machine  cuts  a  circular  groove, 
leaving  a  core  inside  the  tube.  This  core  is  brought  to  the 
surface  with  a  rod,  and  the  powdered  rock  is  washed  out  by 
water  forced  down  the  tube  and  flowing  up  the  sides  of  the 
hole.  The  drill  does  not  have  to  stop  for  cleaning  out — Her- 
man, United  States,  1854. 

242 


APPENDIX 

Photography 

First  photographic  picture,  not  permanent — Thomas  Wedgewood, 

England,  1791. 
Daguerreotype,  first  developing  process — Louis  Daguerre,  France, 

1839- 
First  photographic  portraits,  daguerreotype  process  —  Prof.  J.  W. 

Draper,   United  States,    1839. 

Collodion  process  in  photography — Scott  Archer,  England,  1849. 
Photographic  roll  films — Melhuish,  England,  1854. 
Dry-plate  photography — Dr.  J.   M.  Taupenot,    1855. 
Photographic    emulsion,    bromide    of   silver    in   gelatine,    basis   of 

present  rapid  photography — R.  L.  Maddox,  England,  1871. 
Hand  photographic   camera  for  plates — William   Schmid,  United 

States,  1 88 1. 

Printing 

First  printing  with  movable  types  in  Europe  and  first  printing- 
press — Guttenberg,  Germany,  about  1445. 

Screw  printing-press — Blaew,  Germany,  1620. 

First  newspaper  of  importance — London  Weekly  Courant,  1625. 

Stereotyping,  making  plates  from  casts  of  the  type  after  it  is  set 
up — William  Ged,  Scotland,  1731. 

First  practical  steam  rotary  printing-press,  paper  printed  on  both 
sides,  1800  impressions  per  hour  —  Frederick  Koenig,  Ger- 
many, 1814. 

Printing  from  curved  stereotype  plates — H.  Cowper,  England,  1815. 

Hoe's  lightning  press,  2000  impressions  per  hour — R.  Hoe,  United 
States,  1847. 

Printing  from  a  continuous  web,  paper  wound  in  rolls,  both  sides 
printed  at  once — William  Bullock,  United  States,  1865. 

" Straightline  newspaper  perfecting"  press,  prints  100,000  eight- 
page  papers  her  hour — Goss  Company,  United  States. 

Linotype  machine.  The  operator  uses  a  keyboard  like  that  of  a 
typewriter.  The  machine  sets  the  matrices  which  correspond 
to  the  type,  casts  the  type  in  lines  from  molten  metal,  delivers 
the  lines  of  type  on  a  galley,  and  returns  the  matrices  to  their 
appropriate  tubes.  It  does  the  work  of  five  men  setting  type 
in  the  ordinary  way — Othmar  Mergenthaler,  United  States, 
1890. 

243 


THE  STORY  OF  GREAT  INVENTIONS 


Steam  Navigation 

First  steamboat  in  the  world — Papin,  River  Fulda,  Germany,  1705. 
First  steamboat  in  America — John  Fitch,  Delaware  River,  1783. 
First   passenger   steamboat    in   the   world,    the   Clermont — Robert 

Fulton,  Hudson  River,  1807. 
First  steamer  to  cross  the  Atlantic,  the  Savannah,  built  at  New  York 

— First  voyage  across  the  Atlantic,  1819. 
The  screw  propeller  first   used  on   a  steamboat — John  Ericsson, 

United  States,  about  1836. 

Compound  engines  adopted  for  steamers — 1856. 
First  turbine-steamer,  the  Turbinia — Parsons,  1895. 
First  mercantile  steam-turbine  ship,  the  King  Edward — Denny  and 

Brothers,  England,  1901. 

Steam  Used  for  Power  and  Land  Transportation 

First  steam-engine  with  a  piston — Denys  Papin,  France,  1690. 

First  practical  application  of  the  power  of  steam,  pumping  water — 
Thomas  Savery,  England,  1698. 

Double-acting  steam-engine  and  condenser — James  Watt,  Scotland, 
1782. 

Steam-locomotive  first  used  to  haul  loads  on  a  railroad — Richard 
Trevethick,  England,   1804. 

First   passenger   steam    railway,  the  "Stockton    &   Darlington "- 
George  Stephenson,  England,  1825. 

First  steam  -  locomotive   in  the   United   States,   the   "Stourbridge 
Lion" — 1829. 

Link  motion  for  locomotives — George  Stephenson,  England,   1833. 

Steam -whistle,  adopted  for  use   on  locomotives — George  Stephen- 
son,  1833. 

Steam-hammer — James  Nasmyth,  Scotland,  1842. 

Steam-pressure  gauge — Bourdon,  France,   1849. 

Corliss  engine — G.  H.  Corliss,  United  States,  1849. 

First  practical  steam-turbine — C.  A.  Parsons,  England,   1884. 

Textile  Industries 

Flying  shuttle,   first  important  invention  in  weaving,   leading  to 
modern  weaving  machinery — John  Kay,  England,    1733. 

244 


APPENDIX 

Spinning-jenny — James  Hargreaves,  England,  1763. 

Power  loom — James  Cartwright,  England,  1785. 

Cotton-gin,  for  separating  the  seeds  from  the  fibre,  gave  a  new 

impetus  to  the  cotton   industry.      The  production  of   cotton 

increased   in  five  years   from    35,000    to    155,000   bales  —  Eli 

Whitney,  United  States,  1792. 
Pattern  loom,  for  the  weaving  of  patterns — M.  J.  Jacquard,  France, 

1801. 
Application  of  steam  to  the  loom — William   Horrocks,   England, 

1803. 

Knitting-machine — Brunei,  England,  1816. 
Sewing-machine — Elias  Howe,  United  States,   1846. 
Mercerized  cotton — John  Mercer,  England,  1850. 
Process  of  making  artificial  silk — H.  de  Chardonnet,  France,  1888. 

Wood-Working 

Circular  wood-saw — Miller,  England,   1777. 

Wood-planing  machine — Samuel  Benthem,  England,   1791. 

Wood-mortising  machine — M.  J.  Brunei,  England,  1801. 

Band  wood-saw — Newberry,  England,  1808. 

Lathe  for  turning  irregular  wood  forms — Thomas  Blanchard,  United 

States,   1819. 
Improved  planing-machine — William  Woodworth,   United  States, 

1828. 

Miscellaneous 

First  fireproof  safe — Richard  Scott,  England,   1801. 

Steel  pen,  quill  pen  used  up  to  this  time — Wise,  England,  1803. 

First  life-preserver — John  Edwards,  England,   1805. 

Calculating  machine — Charles  Babbage,  England,  1822. 

First  friction  matches — John  Walker,  United  States,  1827.  Flint 
and  steel  were  used  for  starting  fires  before  matches  were 
invented. 

First  portable  steam  fire-engine — Brithwaite  and  Ericsson,  Eng- 
land, 1830. 

Vulcanizing  of  rubber — Charles  Goodyear,  United  States,  1839. 

Pneumatic  tire — R.  W.  Thompson,  England,  1845. 

Time-lock  for  safes — Savage,  United  States,  1847. 

Match-making  machinery — A.  L.  Denison,  United  States,   1850. 

245 


THE  STORY  OF  GREAT  INVENTIONS 

American  machine-made  watches — United  States,  1850. 

Safety  matches — Lundstrom,  Sweden,  1855. 

Sleeping-car — Woodruff,  United  States,  1856. 

Printing-machine  for  the  blind,  origin  of  the  typewriter — Alfred  E. 
Beach,  United  States,  1856. 

Cable-car — E.  A.  Gardner,  United  States,  1858. 

Driven  well,  an  iron  tube  with  the  end  pointed  and  perforated 
driven  into  the  ground — Col.  N.  W.  Green,  United  States,  1861. 

Passenger  elevator — E.  G.  Otis,  United  States,   1861. 

First  practical  typewriter — C.  L.  Sholes,  United  States,   1861. 

Railway  air-brake,  use  of  air-pressure  in  applying  brakes  to  the 
wheels  of  a  car.  A  strong  spring  presses  the  brake  against 
the  wheels.  Air  acts  against  the  spring  and  holds  the  brake 
away  from  the  wheels.  To  apply  the  brake,  air  is  allowed  to 
escape,  reducing  the  pressure  and  allowing  the  spring  to  act — 
George  Westinghouse,  United  States,  1869. 

Store-cash  carrier — Dr.  Brown,  United  States,  1875. 

Roller  flour-mills — F.  Wegman,  United  States,  1875. 

Kinetoscope,  moving-picture  machine — Edison,   1893. 


INDEX 


AEROPLANE,    184. 

Air-pressure,  23. 

Air-pump,  20. 

Air- ships,  173. 

Air  thermometer,   13. 

Alternating    current,     wonders    of, 

225. 

Amber,  8. 
Ampere,  67,  in. 
Arago,  69. 

Archimedes,  i,  12;  inventions  of,  7. 
Archimedes'  principle,  6,  12. 
Arc  light,  120. 
Armature,  101,  103,  104. 

BALLOONS,  174. 

Barometer,  mercury,  19,  25;   water, 

23- 

Battle  of  Syracuse,  2. 
Bell,  Alexander  Graham,  141. 
Blake  transmitter,  146. 
Bleriot,  190. 
Boyle,  23. 
Branly,    214. 

CANNON  EXPERIMENT, Rumford's,  59. 
Cog-wheels,  first  used,  8. 
Coherer,  214. 
Colors  in  sunlight,  31. 
Condenser  in  steam-engine,  40. 
Conductors,  electrical,  44. 
Controller,  116. 

DANIELL  CELL,  89,  127. 
Davy,  56,  6 1,  96. 
De  Forest,  224. 


Diamonds,  manufacturing,  206. 

Drum  armature,  104. 

Dry  battery,  91. 

DuFay,  45. 

Dumont,   179. 

Duplex  telegraphy,  136. 

Dynamo,  55,  79,  81,  96,  99,  100, 
105,  in;  series  wound,  105 ;  shunt 
wound,  107;  compound  wound, 
108. 

EDISON,  95,  105,  114,  121. 
Electrical  machine,   23,  44,  45,  83. 
Electric  battery,    53,   62,   84,   89. 
Electric  charge,  two  kinds,  45. 
Electric  current,  50,  69,  73,  74,  82, 

96;    magnetic  action  of,   66,   68; 

produced  by  a  magnet,  72. 
Electric  furnace,    205. 
Electricity,   8,    50;  theories  of,   49; 

speed  of,   133. 
Electric  lighting,   97,    118. 
Electric  motor,   71,   97,    in. 
Electric  power,    in. 
Electric  railway,    112. 
Electric  waves,   212. 
Electromagnet,   100,   126,  143. 
Electromagnetism,  65. 

FARADAY,    55,    63,    100,    in;   elec- 
trical discoveries,  64. 
Force-pump,   8. 
Franklin,  43,  45,  46,  65. 


GALILEO,    9,    63;    experiment   with 
falling  shot,   12. 


247 


THE  STORY  OF  GREAT  INVENTIONS 


Galvani,  50. 
Galvanometer,    74 ,   75. 
Gas-engines,  150. 
Glider,   186. 
Governor,  fly-ball,  42. 
Gramme-ring  armature,   103. 
Gravitation,  30. 
Gravity  cell,  91. 
Gray,  Stephen,  44. 
Guericke,  20,  35. 
Gyroscope,  200. 

HEAT,  59. 

Henry,  Joseph,  97,  127. 

Hero,  8,  164;   engine,  164. 

Hiero,  King  of  Syracuse,   i,  6. 

Horse-power,  40. 

Hydraulic  press,  26. 

INCANDESCENT  LIGHT,  121. 
Indicator,  41. 
Induction-coil,  76,  82,  99. 
Induction,  electrical,  74. 
Insulators,  44. 

Inventions  of  the   ancient   Greeks, 
7;   of  the  nineteenth  century,  88. 

KITE  EXPERIMENT,  Franklin's,  46. 
Kites,  27. 

LEYDEN  JAR,  43. 
Lightning-rod,  48. 
Lines  of  force,  99. 


/Liquid  air,   203. 
/  Locomotive,  electric, 


114;  steam,  155. 


MAGDEBURG,  21. 
Magnetic  field,  80,  99. 
Magnets,  8,   130. 
Marconi,   215. 
Mayer,  Robert,  61,  85. 
Mercury  vapor  light,    125. 
Microscope,    18. 
Miner's  safety  lamp,   61. 
Monorail  car,  201. 
Morse,    128. 

NAPOLEON,  62. 
Newcomen,  34,  36. 
Newcomen's  engine,  36. 


Newton,  27. 
Niagara,  227 

OERSTED,  65,  71,  m,  126. 

PAPIN,   35. 

Papin's  engine,  35. 

Pascal,    25. 

Pendulum  clock,  10,  12. 

Perpetual  motion  impossible,  87. 

Phonograph,    147. 

Principle  of  work,  19. 

Prism,  3 1 . 

Pump,  8,  19. 

RADIUM,   232. 

Reis,  Philip,  141. 

Relay,   130. 

Roentgen,  232. 

Royal  institution,  56,  61. 

Rumford,  57,  59. 

Rumford's  cannon  experiment,   59. 

SAFETY-LAMP,   62. 
Screw  propeller,   171. 
Siemens',   100. 
Spinning  tops,  199. 
Steam-engine,  8,  25,  34.    ,  / 
Steam  locomotive,   155. 
Steam  pressure,  23. 
Stephenson,  156. 
Storage  battery,   93. 
Sturgeon,  97,   127. 
Submarines,  190. 
Suction-pump,  8. 
Symmer,  Robert,  49. 

TELEGRAPH,  96,  126;  wireless,  208. 
Telephone,    140;    wireless,   221. 
Telescope,  invention  of,    15;    New- 
ton's 32. 
Tesla,    231. 

Thermometer,  air,   13. 
Torpedo,   192. 
Torricelli,    19,    35. 
Transformer,  80,  82,  99,  227. 
Turbine,    163. 


UNIVERSITY  OF  PADUA,   13. 
University  of  Pisa,  10,  12. 


248 


INDEX 


Valve-gear,  37,  162. 
Volta,  53,  63,  89. 
Voltaic  battery,  53,  89. 

WATER-CLOCK,  8,  29. 
Water-wheel,    165. 
Watt,  James,  34. 


Watt's  engine,  38. 
Wireless  telegraph,   208. 
Wright  aeroplane,   188. 

X-RAYS,   232. 
ZEPPELIN,    180. 


THE   END 


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